CHEMISTRY PAPER 3
PRACTICAL
1989 – 2023
LEAD NOTES QUANTITATIVE AND QUALITATIVE ANALYSIS
QUALITATIVE ANALYSIS
IDENTIFICATION OF IONS
ALSO READ; CHEMISTRY PRACTICALS GUIDE
SETTING TRENDS TABLE
| Year and Question No.( ) | |||||||
| The mole: Formulae and chemical equations TESTED in all years EXCEPT 2002 | |||||||
| Acids, Bases and salts | 90 (c) | 06 (1) | 09 (1) | ||||
| Energy changes in chemical and physical processes | 89 (III) | 94(1) | 95(1) | 97(1) | 00 (2) | 01(III) | 03 (2) |
| 04 (1) | 05(1) | 07 (1) | 08 (1) | 10 (1) | 13(1) | ||
| Reaction rates and reversible reactions | 92 (1) | 99 (1) | 02 (1) | 12(1) | |||
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CHEMISTRY NOTES F1-4: LATEST NOTES
| Questions | Mark schemes | Practical Requirements |
| Practical Experience 1989 | 15 | – | 113 |
| Practical Experience 1990 | 17 | – | 114 |
| Practical Experience 1991 | – | – | – |
| Practical Experience 1992 | 20 | – | 115 |
| Practical Experience 1993 | 23 | – | 116 |
| Practical Experience 1994 | 25 | – | 117 |
| Practical Experience 1995 | 28 | 75 | 118 |
| Practical Experience 1996 | 32 | 77 | 118 |
| Practical Experience 1997 | 35 | 80 | 119 |
| Practical Experience 1998 | 38 | 82 | 120 |
| Practical Experience 1999 | 41 | 83 | 121 |
| Practical Experience 2000 | 43 | 85 | 122 |
| Practical Experience 2001 | 46 | 87 | 123 |
| Practical Experience 2002 | 49 | 89 | 124 |
| Practical Experience 2003 | 51 | 90 | 125 |
| Practical Experience 2004 | 57 | – | 126 |
| Practical Experience 2005 | 58 | 92 | 127 |
| Practical Experience 2006 | 60 | 93 | 128 |
| Practical Experience 2007 | 63 | 99 | 129 |
| Practical Experience 2008 | 66 | 105 | 130 |
| Practical Experience 2009 | 69 | 102 | 131 |
| Practical Experience 2010 | 75 | 107 | 132 |
| Practical Experience 2011 | 81 | 115 | 142 |
| Practical Experience 2012 | 87 | 118 | 143 |
| Practical Experience 2013
Introduction | 87 | 125 | 144 |
The main aim of Chemistry Practical examination is to test a candidates ability to: a). Follow instructions
This book contains 26 practical examinations from 1989 – 2013 as they appeared in during the respective examinations periods. The requirements and preparation procedures for each practical has been provided.
The teacher should give minimal assistance to candidates when carrying experiments to build confidence and enable them make their own observations and inferences. Confidence is only built with constant practice. Candidates are also advised to write the observations as they ‘observe’ during the practical but not the literature they have read from the books.
In experiments involving quantitative analysis the readings show slight variations from the ones given in the answer scheme and also from region to region. Therefore in the calculations and plotting of graphs, the teachers are required to use their school values. Teachers are advised to use the scheme as a guide not as the final correct answer.
QUANTITATIVE AND QUALITATIVE ANALYSIS
The chemistry practical mainly tests the candidates on two parts. Qualitative analysis and quantitative analysis. Students should be exposed to various types of experiments during teaching. Where it is not possible to carry out experiments individually, a well designed demonstration should be undertaken. Teachers should avoid theoretical teaching as this has been manifested many times during the marking of this paper.
Language used to communicate the observations and results must be checked after each practical experiment. Discussion of the results and clear explanations should be given after every experiment. Apparatus must be cleaned to avoid contamination and must be assembled correctly if accurate observations are to be obtained.
Quantitative analysis in chemistry practical examination mainly involves the volumetric analysis. Volumetric analysis is a means of estimating quantities of certain substances (often acids or alkalis) by an analytical process which involves measurement of volumes of liquids using pipettes, burettes and measuring cylinders. Weighing is also involved. It involves the use of the following apparatus
In the K.C.S.E Chemistry practical examination this section requires the candidate to carry out an experiment, record and interpret the data. The interpretation involves calculations and drawing graphs after a candidate has collected the data.
A candidate who is not sure with the calculations after collecting the data is advised to record all his data in the table (s) provided and finally do the calculations. About half of the total marks awarded in this section is mainly from the recording of the data.
It is important for the candidate to spend sometime reading the instructions and the procedure to ensure that all the apparatus and reagents are present and the procedure is clear. After that, the candidate can start going through the procedure step by step and recording the data
In the procedure the key words are normally written in bold letters so that the candidate does not make any mistake.
The common areas in chemistry tested in this section of the practical examination are; a). Moles and molar solution
ii). Redox titration iii). Back titration
To score maximum marks, candidates are required to be perfect in drawing of graphs The mole concept is important to all the calculations involved in the practical examination.
As observed earlier (from the trends table) the topic on energy changes is not properly understood. Questions on energy changes are repeated yearly. More time should be allocated to its teaching and students allowed to carry out experiments on heat changes. Heats of displacement, solution are quite easy to determine. Students should be allowed to determine them. More examples on calculations involving energy changes should be given to students for practice.
|
This involves the identification of various ions in a substance. The tests in this section have been kept as simple as possible to enable the learner understand he/she is doing. To avoid these complex reacts the scheme has been restricted to the detection of the following ions;
|
NH +, K+, NA+, LI+, Ca2+, Ba2+, Al3+, Zn2+, Fe2+, Fe+3,
Pb2+,Cu2+, CO 2-, HCO3-, SO2-3, NO –, Cl–, Br– and I–.
|
This section also tests candidates on identification of organic compounds and their characteristics. When doing the practical examination. Work systematically through the experiments, in the order they are given, writing your observations and deductions as you go along.
If you are unable to make sense of a particular reaction, leave it after recording your observations and move on to the next test or experiment. Do not waste time. You should have time at the end to go over your work, correcting mistakes and checking for anything you think you have missed. Follow the instructions and the procedure carefully.
Observations are changes you see when you carry out a test or experiment. Observations are;
Do not waste time testing for gases unless you know a gas is being produced or unless its indicated in the instructions that test for and identify any gas being produced.
iv). Effect on moist litmus papers
|
Deductions are something you can say about the unknown substances. This can be: i). Anions and cations present in the unknown substance (e.g. SO 2-, or Fe2+ ions)
Deductions must be specific.
|
deduction. For example; you might add Ba(NO3)2 solution to a solution of a substance and see no precipitate. From this you can deduce that there is no sulphate, SO 2-, present (otherwise a white precipitate would be seen)
Your
deduction is what type of a substance has produced the gas. For example,
if you add acid to a solid and observe carbon (iv) oxide then a carbonate is present.
this, you may miss important observations and deductions in other tests, often need the deductions from earlier test to make sense of later tests.
The two common reagents used in the identification of cations are: i). Sodium hydroxide solution
ii). Aqueous ammonia
However, other reagents like dilute hydrochloric acid or an aqueous solution of soluble chloride e.g. sodium chloride and dilute sulphuric acid or an aqueous solution sulphate
e.g. sodium sulphate are use to identify some cations.
In most cases candidates are required to prepare small quantities of solution in a boiling tube or test tube for the unknown substance. If the substance is being tested is insoluble in water, dilute hydrochloric acid is added to the substance. If the solids still will not dissolve it is probably a lead salt and dilute nitric acid must be used.
For the identification of ions to be done the compound must be in aqueous form. The alkali is first added drop wise while the candidate records the observation and then in excess again and observation recorded.
Addition of Sodium Hydroxide Solution to a Solution in a Test Tube
| Test | Observation | Inference |
| Add a few drops of NaOH solution drop wise until in excess | a). No precipitate formed | Zn2+, Al3+, Pb2+, Mg2+, or Ca2+ absent. |
| b). White precipitate , insoluble in excess of NaOH(aq) | Ca2+ or Mg2+ present | |
| c). White precipitate, soluble in excess NaOH (aq) forming a colourless solution. | Pb2+,Al3+ or Zn2+ present | |
| d). Green precipitate which turns brown on exposure to air. | Fe2+ present |
| e). Brown precipitate insoluble in excess NaOH(aq) | Fe3+ present | |
| f). A blue precipitate is formed insoluble in excess NaOH | Cu2+ ions present |
Addition of aqueous ammonia to a salt solution in a test tube
| Test | Observation | Inference |
| Add a few drops of NH3(aq) solution until in excess | a). No white precipitate formed | Ca2+ present/ Na+, K+, NH + 4 |
| b). White precipitate , insoluble in excess of NH3(aq) | Mg2+,Pb2+ or Al3+ present | |
| c). White precipitate, soluble in excess NH3(aq). | Zn2+ present | |
| d). Green precipitate insoluble in excess | Fe2+ present | |
| e). Brown precipitate insoluble in excess | Fe3+ present | |
| f). Pale blue precipitate; which dissolves to form a deep-blue solution in excess NH3(aq) | Cu2+ present |
Addition of Dilute Hydrochloric Acid or Sodium Chloride Solution
| Test | Observation | Inference |
| Add a few drops or (a known volume) of dilute HCl or NaCl(aq) to a solution in a test tube.
‘’ ‘’ ‘’ ‘’ ‘’ | a). White precipitate formed | Pb2+, Ag2+ ionspresent. |
| b). No white precipitate formed | Pb2+ and Ag+ ions absent |
Addition of Dilute H2SO4 acid or Sodium Sulphate Solution
| Test | Observation | Inference |
| Add a few drops or (known volume) of dilute H2SO4 or NaSO4 to a solution in a test tube.
‘’ ‘’ ‘’ ‘’ ‘’ | a). White precipitate formed | Ca2+, Pb2+ or Ba2+ present. |
| b). No white precipitate formed | Ba2+, Pb2+,or Ca2+, absent |
The presence of some metallic ions can be identified by heating the substance in a flame using a platinum wire or a glass rod
| Test | Observation | Inference |
| Dip a clean platinum wire or a | a). Lilac or purple | K+ present. |
| glass rod into a solution of salt | /orange flame | |
| b). Golden yellow flame | Na+ present | |
| c). Crimson flame | Li+ present | |
| d).Brick-red flame | Ca2+ present | |
| e).Green-blue flame | Cu2+ present |
Identification of Anions
The substances to be identified must be in aqueous form before the reagents are added The anions are commonly identified by the use of dilute acids e.g. HCl acid. Precipitation reactions with reagents listed in the table below are used as confirmatory tests.
| Test | Observation | Inference |
| 1). Add dilute acid e.g. HCl to a solution in a test tube | Effervescence /bubbles of a gas are produced. | CO 2- or HCO – 3 3 SO2-3 present |
| 2). Add barium Chloride or Barium nitrate solution to a solution in a test tube followed by dilute HCl acid | White precipitate formed which is insoluble in dilute HCl acid | SO 2- present 4 |
| 3). Add barium Chloride or Barium nitrate solution to a solution in a test tube followed by dilute nitric acid or dil. HCl respectively | White precipitate is formed which dissolves on the addition of the acid | SO 2- or CO 2- 3 3 present |
| 4).Acid lead (II) nitrate to a solution in a test tube followed by dilute HNO3 acid | White precipitate formed which dissolved on boiling | Cl– present |
| b).White precipitate insoluble on boiling | SO 2- or CO -2 4 3 present | |
| c).Pale cream precipitate formed. | Br– present | |
| d).Yellow precipitate formed | I– present | |
| 5).Add a small quantity of cold, iron (II) sulphate solution. Gently pour concentrated H2SO4 acid down the side of the tube. | A brown ring forms in the junction of the two layers | NO – present 3 |
| 6). Add dilute acid to a substance in test tube Test with acidified KMnO4 solution or acidified K2Cr2O7 | A gas with a smell of rotten egg evolved Gas blackens the lead ethanoate paper or lead (II) nitrate solution. | S2- present |
| 7). Add dilute acid to a substance in test tube Test with acidified KMnO4 solution or acidified K2 Cr2 O7 | Effervescence (bubbles of a colourless gas Pungent smell KMnO4 turn from purple to colourless | SO 2- present 3 |
| K2Cr2O7 turn from orange to green |
When heating solid substances always makes sure that the test-tube is clean and dry.
| Test | Observation | Inference |
| Heat a small amounts of the solid in a clean and dry test tube and test for any gas or gases evolved | a). Colourless liquid formed on cooler part or upper part of test tuber OR vapour condenses to a colourless liquid | Hydrated salt or a hydrogen -carbonate or hydroxide |
| b). Colourless gas which gives a white precipitate with lime water | CO 2- /HCO–3 present 3 | |
| c).Colourless gas that relights glowing splint | Nitrate of potassium or sodium | |
| d).Pungent smell; dark brown gas which turns moist blue litmus red | NO – present (except those 3 of Na and K) | |
| e). Pungent smelling gas which turns red litmus blue. | NH + present 4 | |
| f).Sublimation | Possibly NH + 4 |
The usual method of testing for an oxidizing agent is to mix it with a substance which is easily oxidized (i.e. a reducing agent) and which gives a visible change when the reaction takes place. Similarly, a suspected reducing agent is added to an oxidizing agent which undergoes a visible change when reduced.
| Test | Observation | Inference |
| 1. Oxidising agents a). Test with moist starch- potassium iodide paper | Papers turns blue-black | I–ions are oxidized to I2: which then react with starch |
| b). Warm with Conc. HCl | Cl2(smell, bleaches moist litmus paper | Cl– Oxidised to Cl2 |
| 2. Reducing agents a).Add acidified KMnO4 solution | Purple solution is decolorized | Purple MnO –(aq) reduced to 4 colourless Mn2+(aq) ions |
| b). add acidified K2Cr2 O7(aq) | Orange solution turns green | Cr2 O 2- ions are reduced to green 7 Cr3+(aq) ions |
| c). Add a solution of an Iron(III)salt | Yellow solution turns pale Green | Fe3+(aq) ions reduced to Fe2+ions |
| Test | Observation | Inference |
| Add acidified KMnO4 solution to a solution in a test-tube | The purple KMnO4 turns colourless or decolourised | SO 2- ions present OR unsaturated 3 organic compound OR a reducing agent |
| Add acidified K2Cr2O7 solution to a solution in a test tube | It turns green or colour changes from orange to green | 2- SO3 ions present OR unsaturated organic compound OR a reducing agent |
| Add bromine water to a solution in a test tube | It is decolourised or turns colourless | SO 2- ions present OR unsaturated 3 Organic compound OR a reducing agent |
| Add chlorine water to a solution in a test tube. | Brown solution/yellow solution | Br– of I– present |
| Add bromine water to a solution in a test tube | Brown solution/black precipitate | I– present |
Candidates are advised that MARKS are only earned if observation is correct and the scientific language used to describe that observation. It should be known that if the observation is wrong or correct scientific language is not used, then all the marks will be lost.
React the hydrochloric acid solution W9 with metal M and determine the mass per unit length of metal M.
I Fill a burette with solution W11, pipette 25.0cm3 of solution W12 into a conical flask. Titrate using phenolphthalein indicator. Record your results in Table A below;
| 1st | 2nd | 3rd | |
| Final Burette Reading | |||
| Initial Burette Reading | |||
| Titre (cm3) |
(5 marks)
(C=12, H=1, O=16) (1 mark)
(2
marks)
Fill a burette with solution W10, pipette 25.0cm3 of solution W12 into a conical flask. Titrate using phenolphthalein indicator. Record your results in Table B below.
| 1st | 2nd | 3rd | |
| Final Burette Reading | |||
| Initial Burette Reading | |||
| Titre (cm3) |
(5 marks)
| 1st | 2nd | 3rd | |
| Piece of metal M | |||
| Highest temperature | |||
| Initial temperature |
| Change in temperature, ∆T |
(5 marks)
| Observation | Deduction | ||
| a). | Place half a spatula end ful in a dry test-tube and heat gently first and then strongly |
(1 mark) |
(1 mark) |
| b). | To about half a spatula endful in a test tube add about 1cm3 of dilute hydrochloric acid |
(1 mark) |
(1 mark) |
| c). | Place a half a spatula end- ful in a test tube and about 6cm3 of distilled water and shake well. Divide the solution into two portions. | ||
| i). | To the first portion add dilute sodium hydroxide dropwise until in excess. Warm the resulting mixture gently then strongly. |
(2 marks) |
(2 marks) |
| ii). | To the second portion add aqueous ammonia dropwise until in excess. |
| (1 mark) | (1 mark) |
You are required to:
| Trial | 1st | 2nd | 3rd | |
| Final Burette reading | ||||
| Initial burette reading | ||||
| Titre (cm3) |
Average titre =………………………………………………………………….. cm3
(Show the value s being averaged) (1 mark)
Calculations:
Record the readings in the table below. Repeat to obtain three accurate readings.
Temperature of solution of Solid D =……………………o C (1 mark) Table B.
|
(6 marks)
Average titre=……………………………………………………………
(Show the values being averaged) (1 mark)
(1 mark)
(1 mark) iii). Given that the molecular formula of acid D is C7H6O2, calculate the solubility of the acid in grammes per 100cm3 of water (C=2, H=1, O=16).
(2
marks)
You are provided with a solid Q. Carry out the tests below and record your observations and inferences in the spaces provided on the table below. Test for any gas (es) produced.
Table
| Test | Observations | Inferences | |
| a). | Place a spatula endful of Solid Q in a boiling tube and add about 20cm3 of distilled water. Shake well. Use about 2cm3 portions of the solution for the tests below |
(1 mark) |
(1 mark) |
| i). | Test the pH with a pH paper | (1 mark) | (1 mark) |
| ii) | Add a spatula endful of sodium hydrogen carbonate | (1 mark) | (1 mark) |
| iii). | Add two drops of potassium manganate (VII)solution | (1 mark) | (1 mark) |
| iv). | Add two drops of bromine water and warm the solution then shake it well | (1 mark) | (1 mark) |
| b). | Place a little of solid Q in a crucible (a crucible lid or a |
| metallic spatula) and ignite it. | (1 mark) | (1 mark) | |
| c). | Place about 4cm3 of ethanol in a test tube, add two drops of concentrated sulphuric acid then add a spatula endful of Solid Q. Warm the mixture carefully. Shake well and pour the mixture into about 20cm3 of cold water in a boiling tube. Note any smell |
(1 mark) |
(1 mark) |
You are provided with:
You are required to find out the effect of the concentration of potassium iodate, C2, on the rate of reaction with acidified sodium hydrogen sulphite, C3.
NB: The end-point for the reaction of potassium iodate with acidified sodium hydrogen sulphite is detected by the formation of a blue- coloured complex using starch indicator.
table 1 into six dry test-tubes. Using a 10cm3 measuring cylinder, add distilled water to the test-tubes as shown in table 1.
| Test-tube | Volume of C2 and water |
| i). | 10cm3 of C2 +0 cm3 distilled water |
| ii). | 8cm3 of C2 + 2 cm3 distilled water |
| iii). | 6cm3 of C2 + 4cm3 distilled water |
| iv). | 4cm3 of C2 + 6 cm3 distilled water |
| v). | 3cm3 of C2 + 7 cm3 distilled water |
| vi). | 2cm3 of C2 + 8 cm3 distilled water |
Record the time in Table II
Repeat this procedure using the other solutions prepared in (a) above and complete Table II
| Volume of C3 (cm3) | Volume of C4 (drops) | Volume of C (cm3) | Volume of distilled water (cm3) | Time taken for blue colour to appear (seconds) |
| 10 | 3 | 10 | 0 | |
| 10 | 3 | 8 | 2 | |
| 10 | 3 | 6 | 4 | |
| 10 | 3 | 4 | 6 | |
| 10 | 3 | 3 | 7 | |
| 10 | 3 | 2 | 8 |
(6 Marks) c). On the grid below plot a graph of volume (vertical axes) of solution C2 used versus time. (5 Marks)
You are required to determine the value of n in compound C6 Na2B4O7. nH2O.
Table III below and repeat the titration carefully to achieve consistent results
Volume of pipette………………………….. cm3
Burette readings
| Titration number | I | II | III |
| Final reading (cm3) | 28.5 | ||
| Initial reading (cm3) | 00.00 | ||
| Volume of C4 use (cm3) | 28.5 |
(5 marks) Average volume of C5 used = ……………………………..cm3 (1 mark)
Given that the ionic equation for the reaction is
B O 2-
+ 2H+(aq) + 5H2O(l) 4H3BO3(aq)
4 7 (aq)
(1 mole of the base reacts with two moles of the acid)
i). Calculate the concentration of C6 in moles per litre. (4 marks) ii). Calculate the relative molecular mass of the basic compound C6.
(2
marks)
iii). Calculate the value of n in the formula Na2B4O7nH2O
(B=10.8, H=1.0, Na=23.0, and O = 16.0). (3 marks)
You are provided with solid C7. Carry out the following tests and record your Observations and inferences in the spaces provided in table IV.
Table IV
| Test | Observations | Inferences | |
| a). | Place a little of solid C7 in a dry test-tube and heat gently. | (1 mark) | (1 mark) |
| b). | Place the remainder of the solid C7 in a boiling tube. Add about 10cm3 of distilled water and shake well to dissolve the solid. Divide the solution into four positions for tests (i) to (iv) below |
( ½ mark) |
(1 mark) |
| i). | To the first portion add a few drops of dilute sulphuric acid. | ( ½ mark) | (1 mark) |
| ii). | To the second portion add dropwise aqueous sodium hydroxide until in excess | ( ½ mark) | (1 mark) |
| iii). | To the third portion add one to two drops of aqueous lead nitrate | ( ½ mark) | (1 mark) |
| iv). | To the fourth portion add a few drops of barium chloride solution | ( ½ mark) | (1 ½ marks) |
You are provided with:
Pipette 25cm3 of solution A into a 250cm3 conical flask, measure 175cm3 of Distilled water using 100cm3 measuring cylinder and add it to solution A in the beaker. Shake well. Label this as solution D. Pipette 25cm3 of solution D into a 250cm3 conical flask and then titrate with solution C using 1 or 2 drops of Phenolphthalein indicator. Record your results in table I below. Repeat the procedure to obtain accurate values.
| Table I | 1st | 2nd | 3rd |
| Final burette reading (cm3) | |||
| Initial burette reading (cm3) | |||
| Volume of solution C used (cm3) |
Calculations:
a). Determine the average volume of solution C used. (1 mark)
(1 mark)
c). Calculate the concentration, in moles per litre of sodium hydroxide in solution A.
(1 mark)
In the process described below, sodium hydroxide reacts with the ammonium Salt B and on boiling the mixture, ammonia gas is expelled. The excess sodium hydroxide is then determined by titrating the monobasic acid, solution C.
Place all the 1.0g of ammonium salt, solid B into 250cm3 conical flask. Pipette 25cm3 of the sodium hydroxide solution A into the conical flask containing solid B. Shake well until all the solid dissolve. Heat the mixture and let it boil for about 10 minutes. Add 50 cm3 of distilled water to the boiled mixture and shake well. Transfer the solution into a 100cm3 measuring cylinder then add distilled water up to the 100cm3 mark. Pour this solution back into the conical flask and label it as solution E. Pipette 25cm3 of solution E into a 250 cm3 conical flask and titrate with solution C using 1 or 2 drops phenolphthalein indicator. Record the results in the table II below. Repeat the procedure to obtain accurate value and complete Table II
| Table I | 1st | 2nd | 3rd |
| Final burette reading (cm3) | |||
| Initial burette reading (cm3) | |||
| Volume of solution C used (cm3) |
Calculations:
(2
marks)
(1
mark)
(2
marks)
of moles sodium hydroxide that reacted with the ammonium salt.
(2 marks) e). Given that one mole of sodium hydroxide reacts with one mole of the
ammonium Salt B, what is the number of moles of salted in 1.0g of Solid B.
(2 marks) f). Calculate the relative formula of mass of the ammonium salt. (2 marks)
You are provided with solid F. You are required to carry out the tests below and write your observation and inferences in the spaces provided. Identify the gas or gases produced.
Table
| Test | Observations | Inferences | |
| Place all the solid F provided into a boiling tube and add distilled water with shaking until the boiling tube is half full. Use about 3cm3 portions of the solution for tests (a) to (d) below. |
(1 mark) |
(1 mark) | |
| a) | To the 1st portion add sodium hydroxide solution drop wise until in excess | (1 mark) | (1 mark) |
| b) | To the 2nd portion add about six drops of barium chloride solution | (1 mark) | (1 mark) |
| c) | To the 3rd portion add three drops of iodine solution | (1 mark) | (1 mark) |
| d) | Dip one end of the filter paper strip provided into potassium dichromate solution and remove it. To the 4th portion add about 1cm3 of dilute hydrochloric acid, shake well, and observe for about 2 minutes. Place the dipped end of the filter paper at the mouth of the test tube and warm the contents of the test tube gently. |
(3 marks) |
(3 marks) |
You are required to determine the value of n in the formula C3H5O (COOH)n of the carboxylic acid E
results in table l below and repeat the titration to achieve consistent results.
Volume of pipette………………… cm3
Burette readings
| Titration number | I | II | III |
| Final reading (cm3) | |||
| Initial reading (cm3) | |||
| Volume of D used (cm3) |
4 marks
(Show how you arrive at your answer)
2 marks
ii). What is the value of n 1 mark
1.0M Sodium hydroxide solution F 0.63M solution of an acid solution G
You are required to determine the molar heat of neutralization of sodium hydroxide with acid G.
a). Place six test-tubes on a test-tube rack. Using a 10cm3 measuring cylinder, measure 5cm3 portions of solution G and place them into each of the six test- tubes.
Measure 25.0cm3 of solution F using a measuring cylinder and place it into a 100cm3 beaker. Measure the temperature of this solution F to the nearest 0.50C and record it in table II.
Pour the first portion of the 5cm3 of solution G from the test-tube into the beaker containing 25cm3 of solution F, stir the mixture carefully and record the highest temperature of the mixture in table II.
Pour the second portion of solution G immediately into the mixture in the beaker, stir carefully and record the highest temperature of this mixture in Table II. Continue this procedure using the remaining portions of solution G to Complete table II.
| 24 | Ch | emToisttaryl Pvoralcutmicael SotfuGdyaPdadcked (cm3) | 19089 | – 52016 | 10 | 15 | 20 | 25 | 30 |
| Volume of F (cm3) | 25 | 25 | 25 | 25 | 25 | 25 | 25 |
| Temperature (0C) |
mark
4 marks
1
Sodium chloride, potassium chloride, calcium chloride and solid H Note: Solid H will also be required for Question 3 (b)
You are required to carry out flame tests on the above solids to identify the flame colour of the cations present in each of them.
Clean a metallic spatula and rinse it with distilled water. Dry the spatula on a Bunsen flame for about 1 minute. Allow it to cool. Place a little of sodium chloride solid of the flame as the solid burns and record it in Table III below. Clean the spatula thoroughly using steel wool, and repeat the procedure using each of the other solids and complete the Table III.
| Solid | Colour of flame |
| Sodium chloride | |
| Potassium chloride | |
| Calcium chloride | |
| Solid H |
4 marks
b). You are provided with solid H. Carry out the tests in table IV below and record your observations and inferences in the spaces provided. Identify
any gas (es) produced.
Table IV
| Test | Observation | Inferences | |
| i). | Place a little of solid H in a dry test- tube and heat strongly | (1 mark) | (1 mark) |
| ii). | Place the remainder of the solid H in a boiling tube. Add about 10cm3 of distilled water and shake well. Divide the mixture into three portions for tests (I to III) below | ||
| I. To the first portion add aqueous sodium hydroxide until in excess | (1 mark) | (1 mark) | |
| II. To the second portion add aqueous ammonia until in excess | (1 mark) | (1 mark) | |
| III. To the third portion add about 1cm3 aqueous sodium chloride | (1 mark) | (1 mark) |
You are required to determine the enthalpy change for the reaction between a). Potassium hydrogen carbonate and hydrochloric acid
|
readings in table I. Table
On the grid provided plot a graph of temperature against time and determine from it the fall in temperature ∆T1. Show the change ∆T1 on the graph
(3
marks)
Fall in temperature ∆T1 (1 mark)
Calculations; use the following information where necessary
(H=1, C=12, O=16, Mg=24, k=39) Assume density of the solutions to be 1.0gcm3
∆H1 = Mass of solution x 4.2 x ∆T1
n1 x 1000
-1
Kjmol
Mass of solution x 4.2 x ∆T2
∆H2 = Kjmol-1
n2 x 1000 (2 marks)
and MgCO4(s) + 2HCl(aq) MgCl2 (aq) + CO2(q) + H2O(l) Given that the enthalpy change, ∆H3 for the process.
KHCO3 (s) KHCO3(aq) = 121 kjmol-1 determine the Enthalpy
change ∆H4 for the reaction represented by the equation
MgCl2(aq) + 2KHCO3(aq) MgCO3(s) + 2KCl(aq) + H2O(l) + CO2(g)
Use the following expression
∆H4=2∆H1 – ∆H2- 2∆H3 (2 marks)
You are provided with solid L. You are required to carry out the tests below and write your observations and inferences in the spaces provided.
a). Describe the appearance of solid L (1 mark) b). Place a little of solid L, in a dry clean test tube and heat strongly
Observations Inferences
(1 mark)
Observations Inferences
(1 mark)
Observations inferences
(1
mark)
You are provided with solid N. You are required to carry out the tests below and record your observations and inferences in the spaces provided. Identify any gases evolved using a glowing splint and litmus paper
a). Describe the appearance of Solid N. (1 mark) b). Place a little of Solid N on a clean metallic spatula and burn it in a
Bunsen flame (1 mark)
mark)
(1
d). Place the remaining solid N in a boiling tube and add about 20cm3 of distilled water. Shake well until all the solid dissolves. Use about 2cm3 portions of this solution for the tests below.
i). Test the 1st portion with red and blue litmus papers Observations Inferences
ii).
To the 2nd portion add a shake well after every drop Observations
(1 mark)
few drops of dilute sodium hydroxide
Inferences
(1 mark)
Observations Inferences
(1 mark)
Observations Inferences
(1 mark)
Fill the burette with solution A.
Pipette 25.0cm3 of solution B into a conical flask. Titrate solution B with solution A until a permanent pink colour just appears. Record your results in table I below. Repeat this procedure to complete table I.
a). Table I
| I | II | III | |
| Final burette reading (cm3) | |||
| Initial burette reading (cm3) | |||
| Volume of solution A (cm3) |
4 marks b). Record average volume of solution A used, V1 cm3
(Show how you arrive at your answer) 1 mark
1 mark
(II) ions, given below, calculate the concentration of manganate (VII) ions in solution A in moles per litre.
MnO4(aq) + 5Fe2+(aq) + 8H+(aq) Mn2+(aq) + 5Fe3+(aq) + 4H2O(l)
Pipette 25.0cm3 of solution C into a conical flask. Heat this solution to about 700C and titrate the hot solution C with solution A until a permanent pink colour just appears. Shake the thoroughly during the titration. Record your results in table II. Repeat this procedure to complete Table II.
| I | II | III | |
| Final burette reading (cm3) | |||
| Initial burette reading (cm3) | |||
| Volume of solution A (cm3) |
marks
4 marks g). Record average volume of solution A used V2=………………… cm3
Show how you arrive at your answer.
1 mark
H2X 2H2O, in the 25cm3 of solution C. 2 marks
(H = 1.0 O=16.0) 3
Record observations and inferences in the table. Identify any gas (es) evolved.
Divide solid D into portions
Observation s Inferences
2 marks 1 mark
ii). Add distilled water to the mixture in (a) (i) above until the test-tube is about half-full. Shake well and filter into a boiling tube. To about 1cm3 of the filtrate in a test-tube add about 1cm3of 2M sodium hydroxide drop wise
Observations 2 marks
Observations Inferences
Observations inferences
31 Chemistry Practical Study Pack 1989 – 2016
Observations inferences
1 mark 1 mark
You are required to determine the concentration of sulphuric acid in moles per litre
Measure 50cm3 of solution F using a measuring cylinder and place it in a 100 cm3 beaker. Stir the solution gently with a thermometer and take its temperature after every half-minute. Record your results in Table I.
After one and half minutes, add all of solid H at once. Stir the mixture gently with the thermometer and record the temperature of the mixture after every half-minute in table I
|
up to the sixth minute. Keep the solution for use in procedure II a). Table I
(5 marks) b). Using the results in table I, determine the highest change in temperature,
∆T for the reaction
∆T………………. (1 mark)
c). Calculate the heat change for the reaction using the expression Heat change = Mass of solution x 4.2 x ∆T Joules
(Assume density of solution = 1.0g/cm3) (3 marks) d). Given that the molar heat of reaction of sulphuric acid with solid H is
323KJ mol-1, calculate the number of moles of sulphuric acid that were used during the reaction (2 marks)
Place all the solution obtained in procedure I in a clean 100m3 measuring cylinder. Add distilled water to make 100cm3 of solution. Transfer all the solution. Transfer all the solution into a beaker and shake well. The resulting solution is ‘solution K’.
Fill a burette with solution G. Pipette 25.0cm3 of solution K into a conical flask. Add 2- 3 drops of phenolphthalein indicator and titrate with solution G. Record your results in table II. Repeat the titration two more times.
| I | II | III | |
| Final burette reading (cm3) | |||
| Initial burette reading (cm3) | |||
| Volume of solution G used (cm3) |
mark)
mark)
(6 marks) e). Determine the average volume of solution G used (1 mark)
(1
(1
(1 mark)
| a). | Place all of solid L in a dry test-tube and heat it until it just turns reddish- yellow at the bottom. Test the gas with a glowing wooden splint. Keep the residue for tests in (b) Observations inferences
(2 marks) |
| b). i). | Allow the residue from (a) above to cool for about three minutes. Add 5-6 drops of concentrated nitric acid, then add distilled water until the test-tube is three quarters full. Filter the mixture into a boiling tube then add more distilled water to the filtrate until the boiling tube is half-full. Shake well. Use the solution obtained for the tests below Observations (1 mark) |
| ii). | To about 2cm3 portion of the solution in a test–tube, add 2M of sodium hydroxide dropwise until in excess Observations inferences (3 marks) |
| iii). | To another 2cm3 of the solution in a test-tube, add aqueous ammonia dropwise until in excess Observations Inference
(2 marks) |
| iv). | To a third 2cm3 of the solution, add a few drops of 2M sulphuric acid
Observations Inferences 1mark 1 mark |
Place all solid M in a boiling tube. Add distilled water until the boiling tube is half- full. Shake the mixture thoroughly until all the solid dissolves. Use the solution for the tests below.
a). Concentration of solution M in moles per litre b). Percentage purity of the carbonate, solid P.
Fill the burette with sodium hydroxide, solution N. Pipette 25.0cm3 of hydrochloric acid, solution M into a conical flask. Add 2-3 drops of screened methyl orange indicator and titrate. (The colour of the indicator changes from pink to green) record your results in table I below. Repeat the titration two more times and complete the table.
| Table | 1 | 2 | 3 |
| Final burette reading | |||
| Initial burette reading | |||
| Volume of solution N used (cm3) |
(4 marks)
What is the average volume of solution N used? (1 mark) Determine;
(1 mark)
Using a measuring cylinder, measure out 100cm3 of solution M into a 250cm3 beaker. Add all of solid P into the beaker containing solution M. Swirl the mixture and allow the reaction to proceed for about 4 minutes.
Label the solution with sodium hydroxide, solution N. Pipette 25.0cm3 of solution Q into a conical flask. Add 2-3 drops of screened methyl orange indicator and titrate. Record your results in table II below. Repeat the titration two more times and complete the table.
| Table II | 1 | 2 | 3 |
| Final burette reading | |||
| Initial burette reading | |||
| Volume of solution N (cm3) |
(4 marks)
What is the average volume of solution N Used? a). Calculate the:
i). Moles of hydrochloric acid in 25.0cm3 of solution Q (2 marks) ii). Moles of hydrochloric acid in 100cm3 of solution Q (1 mark) iii). Moles of hydrochloric acid in 100cm3 of the original hydrochloric
acid solution M. (1mark)
(1 mark)
b). Given that the relative formula mass of the carbonate is 72, calculate the; i). Mass of the carbonate that reacted (1 mark)
ii). Percentage purity of the carbonate, solid P (1 mark)
You are provided with solid S. Carry out the tests below and record your observations and inferences in the spaces provided.
Observations Inferences
in excess
Observations Inferences
(1 mark) (2 marks)
Observations Inferences
(1 mark) (1 mark)
Observations Inferences
(1 mark) (1 mark)
Observations Inferences
(1 mark) (1 mark)
You are provided with solid L. Carry out the tests below and record your observations and inferences in the spaces provided.
Observations Inferences
(2 marks) (1 mark)
Observations Inferences
(1 mark)
Observations Inferences
| 37 | Chemistry Practical Study Pack 1989 – 201 | 6 |
(1 mark) (1 mark)
Place solution E in a burette.
Pipette 25cm3 of solution F into a 250cm3 conical flask. Add two drops of methyl orange indicator and titrate. Record your results in the table below. Repeat the procedure two more times and complete table I.
| I | II | III | |
| Final burette reading | |||
| Initial burette reading | |||
| Volume of solution E used (cm3) |
(3 marks)
ii). What is the average volume of solution E?
You are required to determine the rate of reaction between magnesium and hydrochloric acid at different concentrations
a).
| Test-tube Number | 1 | 2 | 3 | 4 | 5 |
| Volume of solution L (cm3) | 10 | 9 | 8 | 7 | 6 |
| Volume of water (cm3) | 0 | 1 | 2 | 3 | 4 |
| Time taken (sec) | |||||
| Rate of reaction = 1/time |
b). i). Plot a graph of rate of reaction 1/time (y-axis) against volume of solution L (3 marks)
(1 ½ marks)
Observations Inferences
(4½ marks)
i). To the first portion ,add aqueous sodium hydroxide drop wise until in excess.
Observations Inferences
(2½ marks) ii). To the second portion, add two drops of concentrated nitric acid
then add aqueous sodium hydroxide drop wise until in excess Observations Inferences
(1½ marks) iii). I. To the third portion, add 2-3 drops of barium chloride solution
Observations Inferences
(1½ marks)
Observations Inferences
(2 marks)
You are required to standardize the hydrochloric acid, solution M. Procedure
Fill the burette with solution M. Pipette 25cm3 of solution L into a conical flask. Add
three drops of phenolphthalein indicator and titrate with solution M. Record the readings
in table I below. Add 3 drops of methyl orange indicator to the contents of the conical flask and continue titrating with solution M. Record the readings in table II below. Repeat the procedure and complete tables I and II.
a). i). Table I (Using phenolphthalein indicator)
| 1st | 2nd | |
| Final burette reading | ||
| Initial burette reading | ||
| Titre (cm3) |
(3 marks)
Find average titre t1 (½ mark)
…………………………………………………………………..
Table II (Using methyl orange indicator)
| 1st | 2nd | |
| Final burette reading | ||
| Initial burette reading | ||
| Titre (cm3) |
(3 marks)
Find average titre t2 (½ mark)
……………………………………………………………………..
(1 mark)
(1
mark)
Using a measuring cylinder, place 30cm3 of distilled water into a 100cm3 beaker. Stir the
water gently with a thermometer and take its temperature after every half minute. Record the readings in table III below. At exactly two minutes, add all solid G to the water at once. Stir well and take the temperature of the mixture after every half minute up to the fourth minute
Record your results in table III.
Table III a).
| Time (min) | 0 | ½ | 1 | 1 ½ | 2 | 2 ½ | 3 | 3 ½ | 4 |
| Temperature (0C) |
(3marks) b). On the grid provided, plot a graph of time against temperature
Specific heat capacity of solution = 4.2jg-1 k-1) (3 marks)
Shake well. Filter the mixture into a conical flask. Retain both the filtrate and the residue.
Observations Inferences
(2 marks) (1 mark)
Observations Inferences
(2 marks) (1 mark)
Divide the mixture in (b) (i) above into two portions
Observations Inferences
(2 marks) (2 marks)
Observations Inferences
(1 mark) (1 mark)
Observations Inferences
(1 mark) (1 mark)
Observations Inferences
(1 mark) (1 mark)
until in the excess then filter into a clean test-tube.
Observations Inferences
(1 mark) (1 mark)
Solution D prepared by diluting 25cm3 of solution A with distilled water to 150cm3 of solution. You are required to:
Fill a burette with solution B. Pipette 25cm3 of solution D into a 250cm3 conical flask. Add 2 drops of phenolphthalein indicator and titrate with solution B. Record your results in table 1. Repeat the titration two more times and complete the table.
| I | II | III | |
| Final burette reading | |||
| Initial burette reading | |||
| Volume of solution B used (cm3) |
(4 marks)
Using a clean burette, place 16cm3 of solution C into a boiling tube. Take the initial temperature of the solution in the boiling tube and record it in table II. Using a clean measuring cylinder, measure 4cm3 of solution A into 100cm3 beaker and add it to a solution C in the boiling tube. Stir the mixture immediately with a thermometer and record in table II the maximum (final) temperature reached. Repeat the experiment with the other sets of volumes of C and A in the table and complete it. (Rinse the thermometer and the boiling tube with distilled water after each experiment)
| Volume of solution C(cm3) | 16 | 12 | 8 | 6 | 4 | 2 |
| Volume of solution A (cm3) | 4 | 8 | 12 | 14 | 16 | 18 |
| Final temperature (OC) | ||||||
| Initial temperature (0C) | ||||||
| Change in temperature , (∆T) |
(6 marks)
(1 mark)
(2 marks)
Divide solid E into two halves.
| a). Test the first portion with both blue and red litmus papers Observations Inferences (2 marks) |
| b). To the second portion, add three drops of bromine water Observations Inferences (2 marks) |
| c). To the third portion, add 2 drops of acidified potassium permanganate and shake well Observations Inferences (2 marks) |
| d). Warm the fourth portion slightly and add a little solid G, sodium hydrogen carbonate observations inferences (2 marks) |
You are required to determine how the rate of reaction of hydrogen peroxide with potassium iodide varies with the concentration of hydrogen peroxide.
Label two 200ml or 250ml beakers as beaker 1 and beaker 2.
Using a burette, place 25.0cm3 of solution A into beaker 1. Into the same beaker, add 20cm3 of solution B using a 50ml or 100ml measuring cylinder. Shake the contents of beaker 1.
Using a 10ml measuring cylinder, place 5cm3 of solution C into beaker 2 followed by 5cm3 of solution D then 2cm3 of solution E. shake the contents of beaker 2. Pour the contents of beaker 2 into beaker 1 and start a stop clock/watch immediately. Swirl the mixture and let it stand. Note the time taken for the blue colour to appear. Record the time in the space provided for experiment 1 in the table below.
Clean beaker 1. Repeat the procedure with the volumes of water below. Clean beaker 1. Repeat the procedure with the volumes of water, solutions A, B, C, D and E as shown in the table for experiments 2 to 5.
Complete the table by computing 1 sec -1 7 ½ marks)
Time
a).
| BEAKER 1 | BEAKER 2 | |||||||
|
Experiment | Volume of water (cm3) | Volume of hydrogen peroxide, solution A (cm3) | Volume of dilute sulphuric acid, solution B (cm3) | Volume of sodium thiosulphate, solution C (cm3) | Volume of potassium iodide, solution D (cm3) | Volume of starch, solution E (cm3) | Time (sec) | 1 Time sec -1 |
| 1 | 0 | 25 | 20 | 5 | 5 | 2 | ||
| 2 | 5 | 20 | 20 | 5 | 5 | 2 | ||
| 3 | 10 | 15 | 20 | 5 | 5 | 2 | ||
| 4 | 15 | 10 | 20 | 5 | 5 | 2 | ||
| 5 | 20 | 5 | 20 | 5 | 5 | 2 | ||
(2 marks)
at once. Warm the mixture for one minute then shake vigorously for about five minutes. Filter the mixture into a test-tube and use the filtrate for tests
(b) to (e) below.
Observations Inferences
(1 mark) (1 mark)
Observations Inferences
Observations Inferences
(1 mark) (1 mark)
Observations Inferences
(1 ½ marks) (1 mark)
Observations Inferences
(1 mark) (1 mark)
Observations Inferences
(2 marks) (1 mark)
| Observations | Inferences | ||
| 47 | Chemistry Practical Study Pack 1989 – 2016 | ||
(2 marks) (1 mark)
Observations Inferences
(1 mark) (1 mark)
(1 mark) (1 mark)
Observations Inferences
(1 mark) (1 mark)
You are required to determine the number of moles of Q that react with one mole of potassium permanganate.
Place the solution P in a burette. Pipette 25cm3 of solution Q into a 250cm3 conical flask. Titrate solution Q with solution P until a permanent pink colour just appears. Record your results in table I below. Repeat the above procedure two more times.
a). Table I
| I | II | III | |
| Final burette reading | |||
| Initial burette reading | |||
| Volume of solution P (cm3) |
(4 marks) b). Calculate the average volume of solution P used. (1 mark)
(1 mark)
You are required to determine:
Place 30cm3 of distilled water into a 100ml beaker. Measure the initial temperature of the water and record it in the table II below. Add the entire solid S at once. Stir the mixture carefully with the thermometer until all the solid dissolves. Measure the final temperature reached and record it in the table II.
Table II a).
| Final temperature(0C) | |
| Initial temperature(0C) |
(1½ marks) b). Determine the change in temperature, ∆T1 (½ mark)
c). i). Heat change when H2A dissolves in water .assume the heat capacity of the solution is 4.2jg-10c-1 and density is 1g/cm3 (2 marks)
Place 30cm3 of solution T into 100ml beaker. Measure the initial temperature and record
it in the Table III below. Measure 30cm3 of sodium hydroxide, solution R. Add al the 30cm3 of solution R at Once to the solution in the beaker.
Stir the mixture with the thermometer. Measure the final temperature and record it in Table III.
a).
| Final temperature (OC) | |
| Initial temperature (OC) |
(1 mark)
d). Given that
Water
∆H1 is the heat for the reaction H2A(s) 2H+(a(aq)+A2-(aq)
∆H2 is the heat for the reaction 2H+(aq) + 2OH-(aq) 2H2O(l) Calculate ∆H3 for the reaction H2A(s)+2OH–(aq) 2H2O(l)=A2-(aq)
i). Temperature change when magnesium reacts with excess hydrochloric acid. ii). Number of moles of hydrochloric acid that remain unreacted
Using a burette, measure 50cm3 of solution B and place it in a 100 ml beaker. Measure the temperature of solution B in the 100ml beaker and record the value in table 1. Put the magnesium ribbon in the 50cm3 of solution B in the 100ml beaker immediately, start a stop Clock or watch. Stir the mixture continuously with the thermometer making sure that the Magnesium ribbon remains inside the solution as it reacts. Measure the temperature after Every 30 seconds and record the values in table1. Continue stirring and measuring the temperature to complete table 1.
Keep the resulting solution for use in procedure 2 Table 1
(a)
| Time (sec) | 0 | 30 | 60 | 90 | 120 | 150 | 180 | 210 | 240 | 270 | 300 |
| Temperature (0C) |
(5 marks)
(3 marks)
Transfer all the solution obtained in 1 into a 250ml. conical flask. Clean the burette and use it to place 50cm3 of distilled water into the beaker used in procedure 1. Transfer al the 50cm3 of water into the 250ml conical flask containing the solution from procedure1. Label this as solution D. empty the burette and fill it with solution C. Pipette 25cm3 of solution D and place it into an empty 250ml conical flask. Add two drops of phenolphthalein indicator and titrate solution C against D. Record the results in table two. Repeat the titration of solution C against solution D and complete the table 2
| I | II | III | |
| Final burette reading | |||
| Initial burette reading | |||
| Volume of solution C used (cm3) |
(4 marks)
i). Calculate the average volume of solution C used (1 mark) ii). Calculate the number of moles of:
I 0.3M sodium hydroxide used (1 mark) II Hydrochloric acid in 25cm3 of solution D (1 mark)
III Hydrochloric acid in 100cm3 of solution D (1 mark) IV hydrochloric acid in 50cm3 of solution B (1 mark) V hydrochloric acid that reacted with magnesium (1 mark) VI magnesium that reacted (2 marks)
4.2 jg-1deg-1 and density is 1.0g/cm3
2 a). You are provided with solution H, carry out the tests below. Record
your observation and inferences in the spaces provided. Place 3cm3 of the solution H in the boiling tube. Add 12cm3 of distilled water and shake.
Observations Inferences
( 2 marks)
Observations Inferences
(2 marks)
Observations Inferences
(2 marks)
Observations Inferences
( 2 marks)
Observations Inferences
(2 marks)
Carry out the tests on solutions E, F, G and H in order to identify the cation present in the solution H.
Clean one end of glass rod thoroughly. Dip the clean end of the glass rod in solution E.
Remove the end and heat it in the non-luminous part of the Bunsen burner flame. Note the colour of the flame and record it in table 3. Allow the glass rod to cool for about two minutes. Repeat the procedure with solutions F, G and H complete the table 3.
Table 3 i).
| Solution | Colour of the flame |
| E | |
| F | |
| G | |
| H |
Place 150cm3 of tap water in a 200ml or 250ml, beaker. Heat the water to near boiling. Using a test tube holder, immerse the test tube containing solid M into hot water (ensure that half of the test tube is immersed in water) continue heating the water until the solid starts to melt. insert a thermometer into the liquid being formed in the test tube and note the temperature when all the solid has just melted. Record the temperatures in table 1. Remove the test tube from the water and immediately start the stopwatch clock /watch and record the temperature of the contents of the test tube after every half a minute and complete the table. Dip the thermometer into the hot bath to clean it then wipe it with tissue paper.
| Time (Min) | 0 | ½ | 1 | 1 ½ | 2 | 2 ½ | 3 | 3 ½ |
| Temperature (0C) |
You are required to determine the relative formula mass of acid L Procedure
Using a burette, transfer 25.0cm3 of solution K into a 100ml beaker. Measure the
temperature T1 of the solution K and record it in table 2. Pipette 25.0 cm3 of solution L into another 100ml beaker. Measure the temperature T2, of solution L and record it in table two add all the solution K at once to solution L. Stir carefully with the thermometer. Measure the highest temperature, T3 of the mixture and record it in table 2. Repeat the procedure and complete table 2.
| I | II | |
| Initial temperature of solution K T1(0C) | ||
| Initial temperature of solution L t2(0C) | ||
| Highest temperature of mixture T3 (0C) | ||
| Average initial temperature (0C) | ||
| Change in temperature ∆T (0C) |
(5 marks)
(Assume density of solution is 1g/cm3 and the specific heat capacity is 4.2jg-1K-1)
(2 marks)
(2 marks)
b). You are provided with solid Q. Carry out the tests below. Write your observation and inferences in the spaces provided.
Retain the contents of the boiling tube for use in the procedure (e).
substance that dissolves in 100cm3 (100g) of water at a particular temperature.
| Volume of water in the boiling tube (cm3) | Temperature at which crystals of solid A first appear (0C) | Solubility of solid A (g/100 g water) |
| 4 | ||
| 6 | ||
| 8 | ||
| 10 |
rinse both the boiling tube and the thermometer with distilled water and add to the volumetric flask. Add more distilled water to make up to the mark. Label this solution A. fill a burette with solution B. Using the
pipette and pipette filter, place 25.0cm3 of solution A into a
conical flask. Warm the mixture to about 600C. Titrate the hot solution A with solution
B until a permanent pink colour persists. Record your readings in table 2.
Repeat the titration two more times and complete the table2. (Retain the remaining solution B for use in question 3 (b) (i)
| I | II | III | |
| Final burette reading | |||
| Initial burette reading | |||
| Volume of solution B used (cm3) |
and inferences in the spaces provided.
Carry out the following tests and record your observation and inferences in the spaces provided.
You are required to determine the; Concentration of solution A
Enthalpy of reaction between sulphuric acid and substance C
Using a pipette and a pipette filler, place 25.0cm3 of solution A into a 250ml.
volumetric flask. Add distilled water to make 250cm3 of solution. Label this solution D.
Place solution D in a burette. Clean the pipette and use it to place 25.0cm3 of solution B into a conical flask. Add 2 drops of methyl orange indicator provided and titrate with solution D. record your results in table 1. Repeat the titration two more times and complete the table.
Table 1
| Final burette reading | |||
| Initial burette reading | |||
| Volume of solution D used (cm3) |
(3 marks)
Calculate;
i). Average volume of solution D used (1 mark) ii). Concentration of sodium carbonate in solution B
(Na=23; 0; O=16; 0, C= 12.0) (1 mark)
Label six test-tubes as 1, 2,3,4,5 and 6. Empty the burette and fill it with solution
Clean the burette and fill it with solution C. From the burette, place 14cm3 of solution C into a boiling tube. Measure the initial temperature of solution C to the nearest 0.50C and record it table 2. Add the contest of test-tube number 1 to the boiling tube containing solution C. stirs the mixture with the thermometer. Note and record the highest temperature reached in table 2. Repeat the process with the other volumes of solution C given in table 2 and complete the table.
| Test-tube number | 1 | 2 | 3 | 4 | 5 | 6 |
| Volume of solution A(cm3) | 2 | 4 | 6 | 8 | 10 | 12 |
| Volume of solution C(cm3) | 14 | 12 | 10 | 8 | 6 | 4 |
| Initial temperature of solution C(0C) | ||||||
| Highest temperature of solution C(0C) | ||||||
| Change in temperature ∆T(0C) |
(6 marks)
Assume the specific heat capacity of the solution is 4.2jg-1 K-1 and density of solution is 1.0 gcm-3. (2 marks)
| a). | Place one half of solid E in a clean dry test-tube and heat it strongly. Test any gases produced with blue and red litmus papers. Observations inferences
(2 marks) (1 mark) |
| b). | Place the other half of solid E in a boiling tube. Add about 10cm3 of |
| distilled water and shake until all the solid dissolves. (Use the solution | |
| for tests (i), (ii), (iii) and (iv). | |
| i). | Place two or three drops of the solution in a test-tube. Add 3cm3 of |
| distilled water. Add two drops of universal indicator to the mixture | |
| obtained and then determine the pH of the mixture | |
| Observations inferences | |
| (1 mark) (1 mark) | |
| ii). | To about 1cm3 of the solution a test–tube, add aqueous ammonia drop– wise until in excess Observations inferences
(1 mark) (1 mark) |
| iii). | To 2cm3 of the solution in a test-tube, add three or four drops of solution G (aqueous potassium iodide) Observations inferences
(1 mark) (1 mark) |
| iv). | To about 1cm3 of the solution a test–tube, add four or five drops of barium nitrate solution. Shake the mixture then add about 1cm3 of dilute nitric acid and allow the mixture to stand for about 2 minutes. Observations inferences
(1 mark) (1 mark) |
| a). | Place three or four drops of liquid F on watch glass. Ignite the liquid using a Bunsen burner Observations inferences
(1 mark) (1 mark) |
| b). | To 1cm3 of liquid F in a test–tube, add about 1cm3 of distilled water and shake thoroughly. Observations inferences (1 mark) (1 mark) |
| c). | To 1cm3 of liquid F in a test–tube, add a small amount of solid sodium carbonate Observations inferences
(1 mark) (1 mark) |
| d). | To 2cm3 of liquid F in a test-tube, add about 1cm3 of solution H (acidified potassium dichromate (VI). Warm the mixture gently and allow it to stand for about one minute of distilled water and shake thoroughly. Observations inferences
(1 mark) (1 mark) |
You are required to determine the enthalpy change ∆H, for the reaction between solid A and one mole of hydrochloric acid.
Using a burette, place 20.0cm3 of 2.0M hydrochloric acid, solution B in a 100ml. Beaker. Measure the temperature of the solution after every half-minute and record the values in table 1. At exactly 2 ½ minutes, add all of solid A to the acid. Stir the mixture gently with the thermometer. Measure the temperature of the mixture after every half-minute and record the values in table 1. (Retain the mixture for use in procedure B).
| Time (min) | 0 | ½ | 1 | 1 ½ | 2 | 2 ½ | 3 | 3 ½ | 4 | 4 ½ | 5 |
| Tem (0C) |
(4 marks)
i). Plot a graph of temperature (Y= axis) against time (3 marks) ii). Using the graph, determine the change in temperature ∆T (1 mark)
iii). Calculate the heat change for the reaction (assume that the specific heat capacity of the mixture is 4.2jg-1K-1 and the density of the mixture is 1g/cm3 (2marks)
Rinse the burette thoroughly and fill it with sodium hydroxide. Transfer all the contents of the 100ml. beaker used in procedure A into a 250ml. volumetric flask. Add distilled water to make up to the mark. Label this solution C. Using a pipette and a pipette filler, place indicator and titrate against sodium hydroxide. Record your results in table 2. Repeat titration two more times and complete table 2.
| I | II | III | |
| Final burette reading | |||
| Initial burette reading | |||
| Titre (cm3) |
Calculate the:
iii). Calculate the enthalpy of reaction between solid A and one mole of hydrochloric acid (show the sign ∆H) (2 marks)
| until no further change occurs. Test any gases produced with both blue and red litmus papers. Allow the residue to cool and use it for test (b). Observations inferences
(2 marks) (1 mark) | |
| b). | Add about 10cm3 of 2M hydrochloric acid to the residue and shake for about three minutes. Keep the mixture for test (c) Observations inferences
(1 mark) (1 mark) |
| c). i). | Place about 1cm3 of the mixture in a test-tube and add aqueous ammonia dropwise until in excess Observations inferences
(1 mark) (1 mark) |
| ii). | To the rest of the mixture, add all of solid E provided and shake the mixture well. Observations inferences
(1 mark) (1 mark) |
| a). | Place about one third of solid F on a metallic spatula and burn it using a Bunsen burner Observations inferences
( ½ mark) ( ½ mark) |
| b). | Place the remaining of solid F in a test-tube. Add about 6cm3 of distilled water and shake the mixture well. (Retain the mixture for use in test (c) Observations inferences
(1 mark) (1 mark) |
| c). i). | To about 2cm3 of the mixture, add a small amount of solid sodium hydrogen carbonate Observations inferences
(1 mark) (1 mark) |
| ii). | To about 1cm3 of the mixture, add 1cm3 of acidified potassium |
| dichromate (VI) and warm Observations inferences
(1 mark) (1 mark) | |
| iii). | To about 2cm3 of the mixture, add two drops of acidifies potassium manganate (VII) Observations inferences
(1 mark) (1 mark) |
Prepare a dilute solution of hydrochloric acid and determine its concentration Determine the solubility of solid A in water
Dry conical flask for use in step 4)
Step 1 Place all of solid A in a 250ml dry beaker. Add 100cm3 of distilled water to solid A in the beaker. Using a glass rod, stir the mixture thoroughly for about two minutes. Leave the mixture to stand and proceed with steps 2 and 3.
Step 2 Using a pipette filler, place 25.0cm3 of solution B in a 250ml volumetric flask. Add about 200cm3 of distilled water. Shake the mixture well and add distilled water to make up to the mark. Label this as solution D.
Step 3 Fill a burette with solution C. Using a pipette and pipette filler, place 25.0cm3 of solution D into a 250ml conical flask. Add two drops of the indicator provided and titrate solution D with solution C. Record your results in table 1. Repeat the titration two more times and complete the table 1. Retain the remaining solution D for use in step 5.
Step 4 Filter the mixture obtained in step 1 using filter funnel into a dry conical flask. Lable the filtrate as solution
Step 5 Clean the burette and fill it with solution D. using a pipette and a pipette filler, place 25.0cm3 of solution A into a 250ml conical flask. Add two drops of the indicator provided and titrate solution with solution D. record your results in table 2. Repeat the titration two more times and complete table 2.
| I | II | III | ||
| Final burette reading | ||||
| Initial burette reading | ||||
| Volume of solution C used (cm3) | ||||
| I | II | III | |
| Final burette reading | |||
| Initial burette reading | |||
| Volume of solution D used (cm3) |
(Relative formula mass of metal carbonate = 74, assume density of solution =1g/cm3)
Observations Inferences
(2 marks) (1 mark)
i). To one portion, add aqueous ammonia dropwise until in excess
Observations Inferences
(1 mark) (1 mark)
ii¬). To a second portion, add about 1cm3 of hydrochloric acid solution B.
Observations Inferences
(1 mark) (1 mark)
iii). To a third portion, add two drops of aqueous lead (II) nitrate and heat the mixture to boiling;
Observations Inferences
(1 mark) (1 mark)
Observations Inferences
(1 mark) (1 mark)
Divide the mixture into two portions
PH chart.
Observations Inferences
(1 mark) (1 mark)
Observations Inferences
(1 mark) (1 mark)
Observations Inferences
(1 mark) (1 mark)
dichromate (VI) solution and warm
Observations Inferences
(1 mark) (1 mark)
(1 mark) (1 mark)
You are required to:
Using a pipette and a pipette filler, place 25.0cm3 of solution B into a 250.0ml volumetric flask. Add about 200cm3 of distilled water. Shake well. Add more distilled water to make upto the mark. Label this solution D. Retain the remaining solution B for use in procedure II.
Fill a burette with solution C. using a clean pipette and a pipette filler, place 25.0cm3 of solution D into a 250ml conical flask. Add two drops of phenolphthalein indicator and titrate with solution C. record your results in table
| Table | 1st | 2nd | 3rd |
| Final burette reading | |||
| Final burette reading | |||
| Volume of solution C used (cm3) added |
(4 marks)
of the acid reacts with 3 moles of the base) (1 mark)
iv). Molar mass of the alkanoic acid (1 mark)
Fill a clean burette with solution A. place 5cm3 of solution A into a 100ml beaker. Measure the initial temperature of solution A in the beaker record it in table II. Using a 10ml or a 100ml measuring cylinder, measures 25cm3 of solution B. add it to solution A in the beaker and immediately stir the mixture with the thermometer. Record the maximum temperature reached in table II. Repeat the experiment with other sets of volumes of solutions A and B complete the table.
| Volume of solution A (cm3) | 5 | 9 | 13 | 17 | 21 | 25 |
| Volume of solution B (cm3) | 25 | 21 | 17 | 13 | 9 | 5 |
| Maximum temperature (0C) | ||||||
| Initial temperature (0C) | ||||||
| Change in temperature, ∆T |
(6 marks)
Cary out the tests below and write your observations and inferences in the spaces provided
Observations Inferences
(1 mark) (2 marks)
Observations Inferences
(1 mark) (1 mark)
and shake well. Add 4 drops of this solution to about 2cm3 of solution E in a test-tube.
Observations Inferences
(1 mark) (1 mark)
Observations Inferences
(1mark) (1 mark)
Observations Inferences
(1 mark) (1 mark)
Observations Inferences
(1 mark) (1 mark)
Observations Inferences
(1 mark) (1 mark)
| I | II | III | |
| Final burette reading | |||
| Initial burette reading | |||
| Volume of solution A used (cm3) |
(4 marks)
Add 2 drops of phenolphthalein indicator to the contents of the first conical flask prepared in procedure I and titrate with solution A. Record your results in Table 2. Repeat the procedure with the contents of the second conical flask and complete the table.
| 1st Conical flask | 2nd Conical Flask | |
| Final burette reading | ||
| Initial burette reading | ||
| Volume of solution A used (cm3) |
(3 marks)
Calculate the: –
(2 marks)
Observations Inferences
(2 marks) (1 mark)
(ii) Place the rest of solid D in a boiling tube. Add about 10cm3 of distilled water. Shake well.
To a 2cm3 portion of the solution, add about 1cm3 of hydrogen peroxide and shake well. To the resulting mixture, add aqueous sodium hydroxide drop wise until in excess.
(1 mark) (1 mark)
Divide solution E into two observations.
(1 mark) (2 marks)
(1 mark) (1 mark)
| I | II | III | |
| Final burette reading | |||
| Initial burette reading | |||
| Volume of solution B used (cm3) |
(4 marks)
| Test-tube number | 1 | 2 | 3 | 4 | 5 | 6 |
| Volume of distilled water (cm3) | 0 | 2 | 3 | 5 | 6 | 7 |
| Volume of solution A (cm3) | 10 | 8 | 7 | 5 | 4 | 3 |
| Time (seconds) | ||||||
| Rate = 1/Time (S-1) |
a). Plot a graph of rate (y-axis) against volume of solution A. (3 marks) b). What time would be taken for the blue colour to appear if the experiment
was repeated using 4 cm3 of distilled water and 6 cm3 of solution A?
(2
marks)
Place all of solid E in a boiling tube. Add 20 cm3 of distilled water and shake until all the solid dissolves, label the solution as solution E. Use solution E for experiments (i) and (ii).
(1 mark) (1 mark)
| III. | (1 mark) Two drops of barium nitrate; Observations | (1 mark)
Inferences |
| IV. | (1 mark) Two drops of lead (II) nitrate; Observations | (1 mark)
Inferences |
(1 mark) (1 mark)
(2 marks) (1 mark)
(1 mark) (1 mark)
(1 mark) (1 mark)
ii). Place all the remaining residue into a boiling tube. Add about 10cm3 of distilled water and shake thoroughly. Retain the mixture for the tests in (C).
(½ mark) (½ mark)
carbonate
(1 mark) (1 mark)
(1 mark) (1 mark)
OCTOBER / NOVEMBER 2013
Using a burette, place 50.0cm3 of solution A in a 100ml beaker. Measure
Using a burette, place 50.0cm3 of solution A in a 100 ml beaker. Measure the temperature of the solution and record it in table I below. Add all of solid B provided at once and start a stop watch. Stir the mixture thoroughly with the thermometer and record the temperature of the mixture after every one minute in the table. Retain the mixture for use in procedure II below.
| Time (Min.) | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
| Temperature (0C) |
solution is 4.2Jg-1 K-1; Density of the solution is 1 gcm3).
(2
marks)
Carefully decant the mixture obtained in procedure I into a 250ml volumetric flask. Add
about 10cm3 of distilled water to the residue in the 100 ml beaker. Shake well, allow the mixture to settle and carefully decant into the volumetric flask. Immediately, add about 50cm3 of 2M sulphuric (VI) acid to the mixture in the volumetric flask. Add more distilled water to make 250.0 cm3 of solution. Label this as solution D.
Fill a burette with solution C. Using a pipette and pipette filler, place 25.0cm3 of solution D into a 250 ml conical flask. Titrate solution D against solution C until the first permanent pink colour is obtained. Record your results in table 2 below. Repeat the titration two more times and complete the table. Retain the remaining solution C for use in question 3.
| I | II | III | |
| Final burette reading | |||
| Initial burette reading | |||
| Volume of solution C used (cm3) |
(4 marks)
| Observations | Inferences |
| (1 mark) | (1 mark) |
| Observations | Inferences |
| (1 mark) | (1 mark) |
|
obtained in (a) above, add about 3cm3 of aqueous ammonia (Excess).
| Observations | Inferences |
| (1 mark) | (1 mark) |
| Observations | Inferences |
| (1 mark) | (1 mark) |
| Observations | Inferences |
| (1 mark) | (1 mark) |
| Observations | Inferences |
| (1 mark) | (1 mark) |
| Observations | Inferences |
| (1 mark) | (1 mark) |
| Observations | Inferences |
| (1 mark) | (1 mark) |
| Observations | Inferences |
| (1 mark) | (1 mark) |
CO-ORDINATED MARK SCHEMES
NOVEMBER 1995 MARK SCHEME
1.
| Time (min) | 0 | ½ | 1 | 1 ½ | 2 | 2 ½ | 3 | 3 ½ | 4 | 4 ½ | 5 |
| Temperature (0C) | 23.5 | 23.5 | 23.5 | 23.5 | 23.5 | 15.5 | 16.0 | 16.5 | 17.0 | 17.5 |
Table I (3 Marks)
ii).Readings between 3 -5 min should use continuously (½)
NB; Reaction is endothermic hence temperature must drop in minute 3. If not penalize ½ mark
Temp
Fall in temperature ∆T1=……………. 15 – 0 – 23.5 = – 8.50C
(1 mark)
Graph I (3 Marks)
Scale (sc) – ½ – plots should cover (4 ½ x 3 ½ squares) or more
Plots (Pt) – 1 – if 3 readings incorrect give ½ but if more than 3 incorrect (award 0) If correct scale intervals correct only.
Lines (Lns) – 1 – ½ (for each line) lines should pass through at least three points for each line Xtrapolation (ext) – ½ – for the second line extended downwards
∆ T1 = 1 – a). show ∆T1 on graph at 2 ½ minute ( ½ mark) b). Ignore sign of ∆T value
a). i). n1 = 2/100 = 0.02
Penalize ½ mark for wrong units i.e. m or M. Accept figure continuous units.
If wrong RFM used but shown how found, penalize ½ and mark answer if correct (using wrong RFM)
ii). Mass of solution x 4.2 x ∆T1
∆H1 n1 x 1000
-1
Kjmol
Same as for graph I For correct substitution of
∆T1 and n1
Size 3 ½ x 3 ½ sq
Correct answer should
Correct answer
Be within +2 units correct in the 1st D.C.P (otherwise penalise ½) Have correct sign (+ve) (otherwise per ½ mark)
Penalized ½ if wrong units used – accept lack of units (on second line only)
= 0. 012
Accept answer to 3 or 4 D.C.P only (Not 2 d.c.p)
If RFM is wrong (but shown it was calculated) Penalize ½ mark and mark answer if
correct using
the wrong RFM
ii). For correct subt of n2 + ∆T2 = Correct answer
Answer should be correct to within 12 units in 1st D.C.P
Answer should bear correct sign (-ve) otherwise penalize ½ mark Accept units missing otherwise penalize ½ mark for wrong units used.
e.g ∆H4 = 2 (26.8) – (- 43.8) – 2(121)
= – 144.6 kj/mol
1 mark – for correct answer Penalize ½ mark for wrong sign on answer
Award 0 marks for wrong substitution or wrong sign transferred with ∆H in the substitution. Penalise ½ mark for wrong units used
Penalize ½ mark for wrong transfer of any of the ∆H values
9 marks
| 2 (a) | Silvery / shiny grey/ metallic luster silvery white / shining metal Reject shiny, wrong colour etc, silvery white etc | |
| Observations | Inferences | |
| (b) | turns black/grey/white | L reacts with oxygen in air to form oxide or L is oxidize |
| (c) | Effervescence/bubbles/ gas produced / burns with a pop sound | metal L is above hydrogen in the reactivity series/ or mention any metal above H in reactivity series OR just metal up in the series |
| (d) | Effervescence/bubbles/ gas produced/ gas burns with a pop sound. | metal L is above hydrogen in the reactivity series/ or mention any metal above H in reactivity series OR just metal up in the series |
| (e) | Black/grey/dark coating OR deposit or ppt or substance | Metal L is above Lead in reactivity series OR Lead is displaced by L |
9 marks
| 3 (a) | White Crystalline solid/white powder /white solid | |
| (b) | Burns with Lilac /purple/ violet flame / Reject blue flame | |
| (c) | Gas relights burning splint Solid melts forming colourless liquid If melts to colourless solution (Reject if just melts) | Oxygen/O2 evolved possibly KNO3 Accept NaNO3 if not scored in (b) |
| (d)(i) | No visible change no effect on litmus paper | Neutral solution |
| (ii) | No Precipitate / reject no observable change | Zn2+, Al3+, Pb2+, Ca2+, Mg2+ (Any 3 absent) Or K+ , Na+ Present |
| (iii) | No precipitate. | CO 2-, SO 2- OR Cl– absent 3 4 (Any two mentioned) |
| (iv) | – Colourless fumes/gas/effervescence which turns moist red litmus blue – Grey / black mixture/solid precipitate | – NH3 evolved – Solid contains Nitrogen or NO – ions 3 |
NOVEMBER 1996 MARK SCHEME
Principles of averaging
Values averaged must be shown and must be within + 0.20cm3 of each other
= 0.05995 Mol-1
Note: (i) Accept answer given as 0.060 mol-1 but reject 0.06 mol-1
1000
= correct answer
Conditions
Use of 1st Principle Use of Formula Method
|
No of moles of A (in litres) used M2V2 1
= 1/5 x ans in (d)
No of moles of A in 1000cm3 ans (a) x pipette = 5
= 1/5 x ans in (d) x 1000/titre M2 x titre 1
Correct answer M2 = Ans in © x Pipette
5 x titre
Correct answer
Conditions Note
1 mark ans are correct
for wrong arithmetic b). if step (ii) and (iii)are iii). Penalize ½ mark for wrong combined to make M2
units given the subject award 1 mark
iv). Accept rounding of to the for the combined step 3rd and 4th d.p
Procedure II
1000
= correct answer
Conditions
|
No of moles of the dibasic acid in 25cm3 of sol C = 5/2 x ans in (h)
Conditions
Pipette
Conditions
i). Penalise ½ mark for wrong arithmetic if not within +2 units in the decimal place ii). Answer should be written to at least 3 decimal places, unless it divides exactly.
Otherwise penalize ½ mark
iii). Penalise ½ mark for wrong units used
ans in (j) ½ mark
= correct answer ½ mark X + 2 + 36 = RFM of dibasic acid ½ mark X + 38 = RFM of dibasic acid ½ mark Formula mass of X = RFM of dibasic acid – 38 ½ mark
Correct answer
| Observations | Inferences | |
| 2a (i) | Effervescence that increases with heating Green – yellow gas evolved Gas changes moist blue litmus paper red and then bleaches it | Gas evolved is chlorine D is an oxidizing Agent Note: Chlorine is tied to either greenish – yellow Colour of gas or the Bleaching action of the gas |
| (ii) | Colourless filtrate obtained brown ppt that is insoluble in excess alkali formed | Fe3+ ions present |
| b | Effervescence/bubbles/gas evolved gas has no effect on moist litmus paper. Produced gas relights a glowing split | oxygen gas D is a catalyst D is probably MnO2 |
| Note In (a) (i) and (b) above credit ½ mark for ’gas’ given in place of effervescence /bubbles so long as properties of the gas given in the observation column are not contradictory, otherwise no mark for the ‘gas’ | ||
| 3 | Observations | Inferences |
| a) | Melts to a colourless liquid. And burns with a smoky /sooty. Flame Note: accept melts on its own without Mentioning of colourless liquid. Unless contradictory colour given Accept –yellow sooty flame. But not yellow flame | E is an unsaturated organic compound Note:- credit either E has C: H ratio or E contains C=C or –C=C– in place
of ‘’unsaturated’’ unsaturated tied to smoky flame Organic tied to melting & burning |
| b) | Solid E does not dissolve readily solid E is sparingly partially soluble /solid E dissolves H+(aq) ions present red. | E is an organic acid E is an acidic compound hydrated hydrogen ions H+(aq) ions present |
| c) | Solid E dissolved readily in aqueous NaOH | E is organic acid/or E is a carboxylic acid Or Acidic Compound / H+ ions present. |
| d)(i) | Effervescence/bubbles/ gas evolved colourless gas evolved extinguishes a burning / glowing Splint changes moist blue litmus paper Faint red / pink | Organic acid or carboxylic aid or Acidic compound/ H+ ions present |
| (ii) | A sweet smelling substance is formed / fruity smell/ pleasant smell | Ester is formed O E is a carboxylic acid/ R – COOH / – C – OH alkanoic acid |
NOVEMBER 1997 MARK SCHEME
| Time (min) | 0 | ½ | 1 | 1 ½ | 2 | 2 ½ | 3 | 3 ½ | 4 | 4 ½ | 5 | 5 ½ | 6 |
| Temperature (0C) | 20 | 20 | 20 | X | 25 | 29 | 31 | 31 | 33 | 34 | 34 | 34 | 34 |
½ max for each entry Maximum 5 marks
b). ∆T= 34 – 20 = 140C 1 mark
c). Energy change = 50 x 4.2 x 14 (1)
= 2940 Joules (1) 2 marks
d). Moles = 2940 (1)
323 x 1000
= 0.009 moles (1) 2 marks
| I | II | III | |
| Final burette reading (cm3) | 32.8 | 15.9 | 31.9 |
| Initial burette reading (cm3) | 15.8 | 0.0 | 16.0 |
| Volume of solution G used (cm3) | 17.0 | 15.9 | 15.9 |
(6marks)
e). 15.9 + 15.9 ( ½ )
2
= 15.9cm3 ( ½ ) 1 mark
f). 15.9 x 0.5
1000 (1)
= 0.008 moles (1) 2 marks
g). i). Moles of sulphuric acid = 0.008
2
= 0.004 moles ( ½ ) 1 mark
ii). 25cm3 = 0.004 ( ½ )
100cm3 = 0.016 moles ( ½ ) 1 mark
= 0.025 moles ( ½ ) 1 mark
50
= 0.5M (½) 1 mark
| 2 | Observations | Inferences |
| (a) | Colourless gas that relights a glowing splint (1)is produced | oxide present also allow chlorate nitrate, permanganate (1) |
| (b) (i) | Residue turns black Colourless solution after filtration 1 mark | |
| (ii) | White Ppt (½) Soluble in excess ( ½ ) 3 marks | Al 3+ Pb 2+ or Zn2+ (2) |
| (iii) | White Ppt ( ½ ) insoluble in excess ( ½ ) | Pb2+ or Al3– (1) |
| (iv) | White ppt | Pb2+ |
| 3 a) | Decolourise (1) |
– C = C (1) or –OH(1) |
| b) | Decolourise (1) | – C = C present (1) |
| c) | Vigorous effervescence (1) | Solid M is an acid or ROOH (1) |
NOVEMBER 1998 MARK SCHEME
| I | II | III | |
| Final burette reading | 25.40 | 48.00 | 24.40 |
| Initial burette reading | 1.30 | 24.10 | 0.40 |
| Volume of solution N(cm3) | 24.10 | 23.90 | 24.0 |
1 mark for accuracy; 1 table ; 1 use of decimal; 1 averaging; 1 final
Total marks 4 marks
Average of solution N = 24.10 + 23.90 + 24.0 ( ½ mark)
3
= 24.00cm3 1 mark
a). Concentration of solution N = 8.8
40 = 0.22M (½) 1 mark
b). 24.0 x 0.22 = 25M (½) M = 24 x 0.22
25
= 0.21M (½) 1 mark
Table 2
| I | II | III | |
| Final burette reading | 12.50 | 12.50 | 29.40 |
| Initial burette reading | 0.00 | 0.0 | 17.0 |
| Volume of solution N(cm3) | 12.50 | 12.50 | 12.40 |
1 mark for accuracy; 1 table ; 1 use of decimal; 1 averaging; 1 final
Total marks 4 marks
Average of solution N= 12.50 + 12.50 + 12.4 ( ½ mark)
3
= 12.47cm3 ( ½ ) 1 mark
i). 12.47 x 0.22 (1)
1000 = 0.00274 moles (1) 2 marks
ii). 0. 00274 x 4 ( ½ )
= 0.00100 = ans a (i) x 100/25 1 mark
1000 = ans (b) x 100/1000
= -0.021 moles ( ½ ) = ans a (iii) 1 mark
iv). 0.02 – 0.0109 ( ½ )
= 0.01 ( ½ ) = ans (ii) – ans (ii)
= ans a (iv) 1 mark
v). 0.01 ( ½ ) = ans a (i) 2 2
= 0.005 ( ½ ) = ans a (v) 1 mark
c). i). 72 x 0.005 ( ½ ) = 0.36g ( ½)
= 72 x ans a (iv) = ans b (i) ii). 0.36 x 100 ( ½ )
0.5
= ans b (i) x 100
0.5
= 72 % ( ½ ) = ans (ii) 1 mark
| a). | Observations | Inferences |
| Hissing sound White fumes with choking smell that changes Moist blue litmus paper red and red litmus paper remains red | hydrated salt present
(3 marks) |
| Colourless liquid condenses on cool parts of test tube ( ½ ) | ||
| i). | white precipitate ( ½ ) soluble in excess ( ½ ) | Al 3+ (aq) Pb2+ (aq) or Zn(aq)2+ (2marks) for all three 1 mark for two) (3 marks) |
| ii). | white precipitate ( ½ ) Insoluble in excess ( ½ ) | Al3+ ( ½ ) or Pb 2+ ( ½ ) OR Penalise ½ mark each contradiction (2 marks) |
| iii). | No white precipitate (1) Reject no observable change | Absence of SO 2-(aq) CO 2-(aq) or SO 2 (aq) (1 mark 4 3 3 – for all 3 correct ½ mark for 2 correct)Penalize ½ mark each contradiction. (2 marks) |
| iv). | White precipitate (1) | Cl(aq) present (2 marks) |
3.
| a). | Observations | Inferences |
| Hissing /sound White fumes with choking smell changing moist red litmus blue Melts into a colourless liquid White sublimate Extinguishes a burning splint (2 marks for any four observations correct) | NH + (1) 4 Tied to litmus changing to blue
(3 marks) | |
| b). | i). Turns from colourless to green – yellow OR pH 7 -8 | Weekly alkaline (1) Accept neutral (2 marks) |
| ii) White precipitate | L is acidic | |
| c) | – White ppt dissolves on warming – Effervescence | Carboxylic acid; COOH , H+ Accept acidic compound. |
NOVEMBER 1999 MARK SCHEME
1 (a) (i) Table I
Table (T) = 2mks Decimal (D) = 1mk Accuracy (A) = 1mk
Principle of Av (PA) = 1mk Final answer (F) = 1mk
Note: – 3 titration consistent = 2mks
2 titration consistent = 1 ½ mks 2 titrations inconsistent 1mk
1 titration done = 1mk
(ii) Average volume of solution E
(b) (i) No. of moles of basic compound G2X.10 H2O No. of moles of E = titre x 0.099
1000
No. of moles of F = titre x 0.099 x ½
1000
= Ans (4 d.p)
25
= Ans ( 3 dp)
15.3 = Molarity (Ans. (b) (ii) RFM
RFM = 15.3 = Ans
Ans in (b) (ii)
2G = Ans (b) (iii) – 335 G = Ans (b) (iii) – 335
2
= Ans (± 0.5)
T = 5 mks D = ½
A = 1mk (± 5 secs)
T = 1
(b) (i) S = 1 mk C = 1 mk P = 1 mk
Expression t = 1 = ½ mk
Correct value
Rate at 7.5cm3 (½ mk)
– Rate of reaction increases as concentration OR
– Rate is directly proportional to concentration
– Straight line (+ ve gradient) = ½ mk
| 3a). | Observations | Inferences |
| – Light green solid turns brown – Colourless liquid/moisture/ vapour condenses on cooler part of test tube – Pungent gas with irritating smell which changes moist blue litmus paper turns red – Red litmus paper remains 2½mks) | – Fe2+ present – Hydrated salt/ water of crystallization | |
| bi). | – Green precipitate which is insoluble in excess (1mk) | – Fe2+ present (½ mk) |
| ii). | Yellow /brown/Reddish brown solution | – Fe2+ Oxidised to F3+ |
| Brown ppt. Insoluble in excess(1½ marks) | ||
| iv) | – White precipitate | – SO 2-, SO 2-, CO 2- 3 4 3 |
| II | – White ppt remains | – SO 2- 4 |
NOVEMBER 2000 MARK SCHEME
Table I
Table II
Decimal (D) = ½ mark. Accuracy (A) = ½ mark
(iii) I Conc. of Sodium carbonate in moles per litre (RFM Na2CO3 = 106) 5.6 = 0.05283M.
106
Answer given to at least 3 dp. If not, do not award for answer.
Wrong units ½ mark
1000
= 25 x 0.0528
1000
= 0.0013207mol . (at least 4d.p)
Ans (II) x 2 = Ans.
Therefore in 1000cm3 =
Table III
Table (T) = 1 mark
= Ans III x 1000 = Ans 3 d.P Total titre
Accuracy (A)
2nd Trend – t = 2 ½ to t= 4 being constant and lower than between t = 0 to t = 1 ½ = ½ mk.
OR
-t = 3 to t = 4 being constant and lower than between t = 0 to t = 1 ½ = ½ mk
∆ T
Temp 0C
Time (min)
Scale (S) ½ mk ; Labelling (L) = ½ mk ; Plotting (P) ½ mk ; Shape (S) = ½ mk
Moles of G = 3 /101 = 0.0297( 4 d.p)
(ii) Enthalpy of Solution ∆ Hsoln and show sign of ∆ Hsoln Heat absorbed = 30 x 4.2 x ∆ T = Ans.
Heat absorbed by 1 mole = Ans. Above = Ans J/mol
Ans C
Ans in Kj / mol
| 3 | Observation | Inferences |
| (a) | – Blue residue /solid ppt (1mk) – Colourless filtrate | Cu2+ ions present |
| (b) (i) | – White ppt (1mk) – Dissolves in excess (1mk) | |
| (ii) | – White ppt (1mk) – Dissolves in excess (1mk) | Al3+, Zn2+, Pb2+ present |
| (iii) | – White ppt (½ mk) – Insoluble in excess | – Pb2+ , or Al3+ – Zn2+ absent |
| (c) | – No white precipitate is formed | Al3+ present Pb2+ absent |
| (d) | – White Precipitate | SO 2- 4 |
| (e) | – Blue precipitate – Dissolve in excess to form deep blue solution | – Cu2+ present |
NOVEMBER 2001 MARK SCHEME
Moles of HCl = Moles of NaOH Molarity = titre x 0.128 x 1000
1000 x 25
= Ans
Solution A
Molarity of A = Ans in (a) above x 150
25
= Ans
Or
Ans in (a) above x 6 Procedure II, Table II
∆ T (0C)
(d) (i) = A:C = Ans (b) : Ans (c) = 2: 1
(ii) Conc. In moles per litre of the carboxylic acid solution C Moles of A = Ans. b (ii) x Ans (b) above
1000
Moles of C = ½ x moles of A
Molarity = ½ x Ans. b (ii) x Ans (b) x 1000
1000 x Ans (c)
| 2. | Observations | Inferences |
| (a) | – Cracking sound – Colourless liquid forms on cooler | – Hydrated salt – Neutral substance |
| Parts of test tube. – NO effect on both red and blue litmus papers | ||
| b(i) | – White precipitate | Ca2+, Mg2+ or Ba2+ present |
| (ii) | – White Precipitate | Ca2+, Mg2+ or Ba2+ present OR Mg2+ absent ½ mark |
| (iii) | – White precipitate which dissolves on warming | Cl– present |
| 3 | Observations | Inferences |
| a | – Moist blue litmus paper changes to red – Moist on red litmus paper | – Acidic substance / or H+ present |
| b | – Brown bromine water is not decolourised | C = C or C = C – absent
OR Saturated compound present ½ C = C or – C = C – absent OR Saturated compound present ½ Alkene / alkyne absent ½ |
| c | Purple or KMnO4 is not decolorized Purple KMnO4 colour persists | Absence of C = C or R – OH absent |
| d | Effervescence or bubbles of gas OR Fizzing / Hissing sound | Acidic Compound present Or H+ ions |
NOVEMBER 2002 MARK SCHEME
a).
| Vol of A H2O2 | Vol. H2O | Vol of B. H2SO4 | Vol of C Na2S2O3 | Vol of D KI | Vol of E Starch | Time (sec) | 1/time sec | |
| 25 | 0 | 20 | 5 | 5 | 2 | 18 | 56×10-2 | |
| 20 | 5 | 20 | 5 | 5 | 2 | 22.5 | 4.4×10-2 | |
| 15 | 10 | 20 | 5 | 5 | 2 | 29 | 3.4×10-2 | |
| 10 | 15 | 20 | 5 | 5 | 2 | 43.5 | 2.3X10-2 | |
| 5 | 20 | 20 | 5 | 5 | 2 | 90.5 | 90.5 | 1.1X10-2 |
b). ½ for each axis
2 marks for plotting 5p/s correctly
1 mark for best straight line 4 marks
c). 1/time = 1.7 x 10-2(I)
Time = 58.82sec 2 marks
2 marks
| 2 | Observations | inferences |
| a | Shiny metal is coated with a Black/grey substance (½)Colourless filtrate obtained (½) | metal G is more reactive than metal whose ions are In solution F (I) OR displacement reaction Occurred |
| b | No white ppt(1) Or Rej no observable change | Absence of SO 2- CO 2- or SO 2-(ions) 4 3 3 award 2 marks for all 3 Award 1 mark for 2 Award ½ mark for 1 |
| c | White PPt (½) Soluble in excess (½) | Pb2+, Al3+ or Zn2+ as in (b) above 3 marks |
| d | White PPt (½) which dissolves on boiling (I) | Pb2+ (I) present 2 ½ marks |
| e | White PPt (½) colourless filtrate ( ½ ) | Pb2+ confirmed (I) 2 marks |
| f | White PPt (I) Soluble in excess (I) | Zn2+ present (I) 3 marks |
| 3 | Observations | inferences |
| a | Melts ( ½ ) into colourless liquid ( ½ ) burns with a smoky flame (1) | unsaturated organic compound accept long chain hydrocarbon or aromatics |
| b(i) | The purple KMnO4 decolourised/changes to colourless. The colour of KmnO4 changes from purple to colourless (I) 3 marks | Could be an alcohol or unsaturated compound (I) R – OH , – C = C – C = C – 2 marks |
| (ii) | Brown bromine is decolorized/ changes t colourless Decolourised (I) | Unsaturated (I) compound 2 marks |
| (iii) | Turns orange ( ½ ) pH = 5 ½ 2 marks | compound is a weak acid (I) 2 marks |
NOVEMBER 2003 MARK SCHEME
(b) Average volume of solution P 15.0 + 15.0 = 15.0cm3
2
(c) 15.0 x 0.02 = 0.0003 moles
1000
(d) gdm3 = 4.18 x 1000
250
= 16.72gdm3
16.72 from (d) above = 0.060M 278
(e) Moles of Q in 25.0cm3
0.06 x 25 = 0.0015 moles
1000
0.0003
= 5 moles
30 x 4.2 x ∆ T = Ans in J. Or 30 x 4.2 x ∆T = kJ
1000
(ii) Number of moles of acid used (RFM of H2A is 126) 1.9 = 0.01508 moles
126
∆ H c (i) = J/mole Or Kj/mole c (ii)
Procedure II
(a) and (b) as in procedure 1
1000
∆ H2 = C (i) = Ans
C (ii)
Or
60 x 4.2 x ∆ T = Ans. (in J or KJ) C (ii)
∆ H3 = ∆ H2 + ∆ H2 = Ans (-ve kJ /mole)
| 3 | Observations | Inferences |
| (a) | Colourless solution formed | Coloured ions absent e.g Cu2+ , Fe2+, or Fe 3+ absent |
| (b) | No white precipitate formed | Pb2+’ Al3+, Zn2+ , Mg2+ Or Ca2+ absent |
| (c) | White precipitate formed | Cl–, SO 2–, SO 2– , or CO 2+ present 4 3 3 |
| (d) | White precipitate formed dissolves in HCl (aq) | SO 2- or CO 2- present 3 3 |
| (e) | Purple KMnO4 is (aq) decolorized or changes to colourless | SO 2- present Or Reducing 3 |
| (f) | Green solution formed OR Colour changes Orange to green | SO 2- present Or Reducing 3 |
NOVEMBER 2005 MARK SCHEME
| Time (min) | 0 | ½ | 1 | 1 ½ | 2 | 2 ½ | 3 | 3 ½ |
| Temp (0C) | 82 | 73 | 69 | 68 | 68 | 68 | 66 | 65 |
1 Mark fore the two axis
1 mark for all points correctly plotted
1 mark for plot occupying ¾ of the grid provided
2
| I | II | ||
| Initial temperature of solution KT1 (0C) | 26 | 26 | |
| Initial temperature of solution L T2 (0C) | 25 | 26 | |
| Highest temperature of mixture T3 (0C) | 30.5 | 31 | |
| Average initial temperature (0C) | 25.5 | 26 | |
| Change in temperature ∆T (0C) | 5 | 5 | |
| Table 1 ½ mark for each entry | (5 marks) | ||
| a). | Average 5 + 5 = 5 | ||
| 2 | (1 mark) | ||
| b). | Heat change = 50 x 4.2 x 5 (1) | ||
| = 1050 Joules | (2 marks) | ||
143.4 x 1000
= 0.0078125 (2 marks)
d). 25cm3 = 0.0078125 moles
= 0.0078125 x 1000
25
= 0.3125M (2 marks)
e). Relative formula mass of acid L 60 = 0.3125 – (L)
R.F.M
R.F.M = 192 (l)
(2 marks)
| 3 | Observations | Inferences |
| (a) (i) | Cracking sound Colourless liquid Gas with pungent smell Colourless gas is produced which changes moist red litmus paper blue (2 marks for four correct observations | N is hydrated a basic gas is formed ( ½ mark for each) (correct inference) |
| (i) | White Ppt (½) | Al3+ or Pb2+ ions, Mg2+ ions present |
| (ii) | No white precipitate is formed | Al3+ ion ; Mg2+ ion present; Pb2+ ions absent |
| (iii) | White Ppt | SO 2-, SO 2- CO 2- Cl– 1 mark for two (2 4 3 3 marks) |
| (iv) | White Ppt |
| persists (l) | 2 SO4 – ion present –(l) (2 marks) | |
| b(i) | A clear colourless solution (l) | Salt is soluble (l) (2 marks) Acid solution is formed ( 1) |
| (ii) | No effervescence (l) | (H+ absent (l) (2 marks) |
| (iii) | White solid formed (l) Slightly soluble in excess ( ½ ) On addition of NaHCO3 There is effervescence ( ½ ) Colourless gas ( ½ ) Give maximum 2 marks for observations) ( 3 marks) | Acid solution is formed ( 1) |
NOVEMBER 2006 MARK SCHEME
| Volume of water in the boiling tube (cm3) | Temperature at which crystals of solid A first appear ( 0C ) | Solubility of solid A (g/100g water |
| 4 | 66 – 67 | 112.5 |
| 6 | 56 – 57 | 75 |
| 8 | 49 – 50 | 56 |
| 10 | 44 – 45 | 45 |
1 mark for temp value within range
½ mark for each value ± 20C
½ mark for each value of solubility correctly calculated
(ii) – S – 1; P – 1; C – 1
(iii) 63 ± 0.5 0C
| I | II | III | |
| Final burette reading | 24.40 | 48.60 | 26.20 |
| Initial burette reading | 0.00 | 24.40 | 26.40 |
| Volume of solution B used (cm3) | 24.40 | 24.40 | 24.20 |
(Award for each titre value ± of the teachers value
I 24.20 + 24.20 = 24.20cm3
2
II 0.06 x 24.20 = 1.45 x 103 moles
1000
III 1.45 x 10-3 x 5 = 3.63 x 10-3 moles
2
IV 3.63 x 10-3 x 10
= 3.63 x 10-2 moles
= 4.5
x 10-2
= 124
(iii) DxH2O
90 + 18 x = 124
X = 34
= 1.9
= 2
2.
| Observations | Inferences |
| (a) Colourless liquid condenses on cool parts of test tube. White solid remains | Probably hydrated salt/ compound (1) present |
| (b) – Colourless filtrate ( ½ ) – White residue | Compound sparingly soluble |
| (i) Solution turns pink | Compound is basic OH–, HCO3 or CO 2– present 3 OH– present or HCO3 or CO 2- absent. 3 |
| (ii) No effervesnce | |
| (iii) White ppt formed | Ca2+ , Ba2+, Pb2+ present (2mks for all three 1 mk for 2 |
| (iv) No white ppt | Ba2+ present or Ca2+ or Pb2+ |
3.
| (a) Burns with luminous ( yellow, smoky) flame | Unsaturated compound OR Long chain hydrocarbon – C = C – / – C = C – Or Hydrocarbon with |
| high C: H ratio Or aromatic cpd – NB – Each these tied to burning with smoky/sooty flame | |
| (b) (i) Purple Potassium manganate (VII) is Decolourised (changes from purple to colourless | Alkene or alcohol present – C = C – or R – OH |
| (ii) Brown bromine water is decolorized ( Changes from red to Colourless) | Alkene present // – C = C – present |
NOVEMBER 2007 MARK SCHEME
| I | II | III | |
| Final burette reading | 21.8 | 21.6 | 43.6 |
| Initial burette reading | 0.0 | 0.0 | 22.0 |
| Volume of D used (cm3) | 21.8 | 21.6 | 21.6 |
(3 marks)
i). 21.6 + 21.6
2 = 21.6cm3 (1 mark)
Conc. 8 = 0.075M 106
= 0.001875
Moles of H2SO4 = 0.001875
Conc. of H2SO4 = 0.001875 x 1000 21.6
= 0.0868M
iv). 0.0868 x 10 = 0.868M
|
b). i).
(2 marks)
(1 mark)
| ii). | Graph | (3 marks) | |||
| iii). | I | ∆t = 9.5 + 0.10C | (1 mark) | ||
| II | Maximum volume of A = 7.6cm3 + 0.1 | ||||
| iv). | I | Moles of sulphuric acid = 7.6 x 0.868 1000 | |||
| II | Heat evolved | = | = 0.0066 moles 16 x 4.2 x 9.5 | (1 mark) | |
| Molar Heat | =
= | 638.4 joules = 638.4 0.0066 96.727272KJ mol-1 |
(2 marks) | ||
| 2 | Observations | Inferences | |
| (a) | Gas with pungent/irritating/choking smell is produced which changes moist blue litmus paper turns red Colourless liquid formed on cool part of test tube Solid turns reddish brown | hydrated salt acidic gas evolved | |
| (b) (i (ii) | Reddish brown solution pH 1, 2, 3 Brown precipitate insoluble in excess Brown /Black solid formed or solution | strongly acidic Fe3+ | |
| 97 | Chemistry Practical Study Pack 1989 – 2016 | ||
| (iii) (iv) | Changes from yellow to brown White precipitate settles at the bottom of the test tube | Iodide ions/ I– ions present |
| 3 | Observations | Inferences |
| (a) | Clear blue flame | saturated low carbon organic compound ( 2marks) |
| (b) | No separation or forms a solution two liquids are miscible | Mixture is miscible or polar organic compound (1 mark) |
| (c) | No effervescence | Liquid not acidic or absence of H+ (2 marks) |
| (d) | Solution changes from orange to green | F is likely to be Alcohol or R-OH (2 marks) |
NOVEMBER 2008 MARK SCHEME
TABLE 1 (4 Marks)
Award a total of 4 marks distributed as follows
Compare the S.V. to the candidates temperature reading at 2 min and award 1 mark if the reading is within +2.00C of the S.V. otherwise award zero mark
Note
S.V refers to the teacher’s temperature readings at t = 0 min where all the five initial temperature reading are the same or the temperature reading at t=2 minutes in case the 5 initial temperature readings are not the same
Award two halves as follows
Note
– Show the tick accuracy on the table
GRAPH
Award a total of 3 marks distributed as follows
award ½ mark only if both axes are correct labeled (i.e. temperature on vertical and time on horizontal )
Penalties
/not used
Conditions
Note
Penalise fully if any of the above conditions are not met
i). If 10 or 9 points are correctly plotted award 1 mark ii). If 8 or 7 points correctly plotted award ½
iii). If less than 7 points are correctly plotted award 0 marks
99
Temperature (OC)
Chemistry Practical Study Pack
∆T
1989 – 2016
Temp (OC)
Temperatur e ( C)
Temp (OC)
Temp (OC)
Time (minutes)
Temperature (OC)
Temp (OC)
Time (minutes)
Time (minutes)
Table 1
| Time (min) | 0 | ½ | 1 | 1 ½ | 2 | 2 ½ | 3 | 3 ½ | 4 | 4 ½ | 5 |
| Temp (0C) | 18. 0 | 18.0 | 18.0 | 18.0 | 18.0 | X | 13.0 | 13.0 | 13.5 | 13.5 | 14.0 |
Conditions
= 20 x 4.2 x Answer (ii) above(6)
= 504 joules
Or
∆H = MC∆T
= 20 x 4.2 x Answers (ii) above
1000
= Correct Answer
Table 2
| I | II | III | |
| Final burette reading | 16.50 | 32.20 | 32.20 |
| Initial burette reading | 0.00 | 16.00 | 16.00 |
| Titre (cm3) | 16.50 | 16.20 | 16.20 |
Award a total of 5 marks distributed as follows (i) Average Titre = 16. 20 + 16.20 = 16 .20cm3
2
1000
Moles of HCl = Ans I above Or Moles of HCl in 25cm3 of soln = Ans I above.
25
Or
Ans II x 10 = Correct Ans
Conditions
i). Penalise ½ mark for wrong transfer of answer (II) ii). Penalise fully for strange figure
iii). Answer as expected otherwise penalize ½ mark (don’t work at accuracy, d.p) for wrong answer
Notes
IV). 2 x 20
1000 = 0.04
Answer as expected otherwise penalize ½ mark
= Correct Ans
Conditions
Answer (IV) III must be transferred intact otherwise penalize ½ mark for wrong transfer of either of item or both. However for strange figures penalize fully.
Note
ANS v UNITS j Mol- OR Kj Mot Or
Ans v = Ans iii procedure A
: I Mole of HCl = Ans (iii) Procedure A
Ans V
=Correct Ans JMol-1
Or
Ans v = Ans (i) Procedure A (Joules)
; 1 Mole of HCl = Ans (iii) Procedure A
Ans V x 1000
Jmol-1 or KJ mol-1
| 2 | Observations | Inferences |
| a | Green solid turns black/ Green solid forms black solid/ residue ; Colourless liquid forms on the cooler part of the test tube/ Colourless vapour condenses on the cooler part of the test tube ; Blue litmus turns red; Red litmus remains red/ the same colour. Penalise fully for contradiction on colour properties Rej. Colourless liquid condenses / colourless vapour forms/moisture condenses/No effect on red litmus/Red litmus remains the same colour | – Hydrated salt/compound or contain water of crystallization (Tied to colourless vapour condensing) Acidic gas produced (Tied to blue litmus turning red. |
| b | Black solid / residue reacts dissolves to form green solution Or Green solution formed Ignore – No effervescence Rej. Blue solution/ No change/ reaction | Black solid/ residue is basic/ Colored ion present / or Cu2+, Fe2+ ions present |
| c (i) | Blue ppt/ suspension /solid formed / Blue ppt dissolves in excess aqueous ammonia to form a deep blue solution | Cu2+ Present ( tied to blue ppt and deep blue solution Must |
| (ii) | Effervescence occurs / bubbles formed/ Fizzing; Rej hissing/ Brown/ reddish brown solid deposited/ Green solution turns colourless / Test tube becomes warm /hot | E is a metal above copper in the ECS / Metal E displaces copper/ metal E is more reactive than cooper / metal E reduced Cu2+ ions to Cu ( Tied to brown solid deposit) |
| 3 | Observations | Inferences | ||||
| a | Burns with a yellow sooty smoky flame ½ mark Burns with a luminous sooty/smoky flame | – long chain/ unsaturated organic/ hydrocarbon with a high C: H ratio C = C or – C = C ½ marks Reject C = C, C = C Carbon to carbon double or triple bond in words Alkaline /alkaline | ||||
| b | Dissolves/ soluble to form a colourless solution | Polar organic compound Note Accept soluble /substance/salt/compound present | ||||
| c (i) | Effervesnce formed | occurs | or | bubbles | are | R – COOH / H+/ H3O+ Accept – Acidic compound /solution Organic compound ; Carboxylic acid |
| (ii) | Orange colour K2Cr2O7 solution persists / remain the same / orange / orange colour Rej – Yellow used in place of orange K2Cr2O7 not decolourised | R – OH absent Note : Penalise fully if any other functional groups are mentioned | ||||
| (iii) | Purple KMnO4 soln is decolorized or KMnO4 soln changes from purple to colourless Note : Rej Solution remains / becomes / turns colourless |
– C=C- / C = C – present Accept for unsaturated organic compound present | ||||
NOVEMBER 2009 MARK SCHEME
1.
| I | II | III | ||
| Final burette reading | 22.20 | 21.50 | 22.50 | |
| Initial burette reading | 0.00 | 0.00 | 1.00 | |
| Volume of solution C used (cm3) | 22.20 | 21.50 | 21.50 | |
(4 marks)
= 21.50 + 21.50
2
= 21.50 (1 mark)
100cm3 of sodium contains 0.3 moles of NaOH 21.50cm3 of solution contains 0.3 x 21.5
1000
= 0.00645 moles (1 mark) iii). Moles of hydrochloric acid in 25.0cm3 of solution D
= 0.00645 moles (1 mark)
iv). Morality of hydrochloric acid in solution D.
25cm3 of solution contains 0.00645 moles Hcl
0.00645 x 1000
100cm3 of solution contains 25
= 0.25M (1mark)
| |||||||||||||||||||||
Table 2
20.90 + 20.90
(4 marks)
2 = 20.90cm3 (1 mark)
ii). Moles of hydrochloric acid in average volume of solution D used 1000cm3 of solution contains 0.258 moles of HCl
20.90cm3 of solution contains 0.258 x 20.90 moles
1000
= 0.0054 moles (1 mark) iii). Moles of the metal carbonate, solid A in 25.0cm3 of solution A.
Mole ratio of acid to carbonate 2: 1 (1 mark)
½ x 0.0054
= 0.0027 moles (1 mark)
iv). The solubility of the metal carbonate in g/100g of solution mass of carbonate = 0.0027 x 74
in 25.0cm3 of solution = 0.1998g
100g of solution will contain 0.1998 x 100g of carbonate
25
= 0.7992g/100g of solution (1 mark)
Observations Inferences
Colourless liquid hydrated salt/ compound or contains Condenses on the cooler parts of test tube water of crystallization (Tied to
Gas produced forms white Colourless liquid forming after fumes with fumes HCl. (2 marks) Or condensation
|
solid sublimes/forms a white sublimate Ammonia gas (NH + ) present ( tied to white solid formed on the cooler parts gas forming with HCl
of the test tube
b).
for each
Pb2+ in
ii).
Observations Inferences
No white ppt / No white solid Pb2+ absent
No white suspension No effervescence/ No bubbles
or Al3+ present tied to white ppt Note: if a candidate mentions
Rej. No observable change Place of Al3+ present credit ½
|
No ppt / change/reaction CO 2- and SO3 absent Tied to no
No white substance Effervescence. (2 marks)
Colourless soln formed NB. To award ‘Al3+ present it must have
Soln remains colourless been credited in b (i) ; To award
No colour change Pb2+ absent it must have been mentioned as present in b (i); Ignore mention of Ag+ absent
iii).
Observations
White ppt /solid/suspension
Inferences
|
– SO 2- present
without
which does not dissolve on boiling – If a candidate mentions Cl–
|
giving SO 2- present award ½ mark
Penalise fully for any contradictory ion
(1 mark)
Formulae of the ion must be given correctly in all the above inferences. Rej ions given in words only (2 marks)
White solid dissolves to F is a non polar compound
form a colourless solution (1 mark) (1 mark)
Accept a colorless solution formed Without mention of dissolve or soluble For 1 mark
Forms a solution / clear solution without Mention of dissolve or soluble for 1 mk
PH = 7 Neutral solution
(1 mark) (1 mark)
Note: Ignore mention of colour Accpt: Soln neither acidic nor alkaline of mixture; Reject pH range Rej basic used in place of alkaline
ii).
Observations
Inferences
No effervescence/ No bubbles (1 mark)
H+ absent
Accept soln not acidic for ½ mk in the absence of H+ absent
Ignore R – COOH absent
b).
Accept Fizzing used in place of Effervescence or bubbles for
(1 mark)
Does not turn green. Orange Color of K2 Cr2 O7 (1 mark) Note both initial colour and Final colour must be given Otherwise penalize fully Accpt: Orange colour of K2Cr2O7 solution persists / remains;
Rej: Yellow used in place of orange
Inferences
Carboxylic/alkanoic acid preset Or – COOH present/ H+/ H3O+
(1 mark) Inferences
Alcohol absent / R – OH Rej – OH (2 marks)
iii).
Observations Inferences
Bromine water not decolourised Accept yellow/ Orange / red colour of bromine water persists
/ remains (1 mark)
C = C / – C = C – absent
Accept unsaturated organic compound absent for ½ mk. Penalise fully for any contradictory / functional groups
(1 mark)
NOVEMBER 2010 MARKSCHEME
Q1. Table 1………………………. 5 marks
a). Complete table …………………. 1 mark
NOTE; i). In case there was wrong arithmetic /substration in the table, use the correct values in averaging for the final answer.
e.g. 1 S.V = 15.80cm3
Conditions values are 15.4cm3, 15,6cm3, 15.8cm3
Candidates working
Either 15.4 + 15.6 + 15.8
3
= 15.60cm3 (1 mark)
OR 15.4 + 15.6
2
= 15.5cm3 (1 mark)
Examiner to pick = 15.6 + 15.8 = 15.7cm3
2 (1 mark)
2 S.V = 15.50cm3
Candidates values are 15.8, 15.6, 15.6 Candidates working
3 S.V = 15.90cm3
15.6 + 15.6
2 = 15.6cm3 ½ mark
Candidate’s values are 16.0, 15.8, and 15.6 Candidates working
15.8 + 15.6
2 = 15.70cm3
And award 1 mark instead of ½ mark if the candidates value are used
CT – 1; D – 1; A – 1; PA – 1; FA – 1
CALCULATIONS
i). No. of moles of NaOH in 25cm3 of solution B = 2 x 25
1000
Moles of NaOH in 250cm3 of solution D = 2 x 25
1000
Hence Conc. of solution D = 2 x 25 x 1000
1000 250
= 0.200 mols
Or
Conc of solution D = 2 x 25 x 1000
1000 250
= 0.200 mol L
Or
Mc Vc = Md Vd = M1 V1 = M2 V2 /Mg Vg = Md Vd Md (Or M2) or md = 2 x 25
100
Or
Conc of solution D = 2 x 1
10
= 0.200 mol-1
= Ans (II) x 25
1000
Moles of alkanoic acid used = 1/3 x ans (II) x 25
1000
Hence conc of solution C = 1/3 x ans (II) x 25 x 1000
1000 Titre
= correct ans.
OR
Conc of solution C = 1/3 x ans (II) x 25
Titre
= Correct ans.
OR
Ma Va = 1/3 = Ma = 1/3 x ans (II) x 25 MbVb Titre
= correct answer
= 25.0
Ans (III)
= Correct answer
Note: i). Penalise ½ mark for wrong transfer of ans (III) otherwise penalize fully for strange figures used.
Procedure
GRAPH
Table II…………………….. 6 marks
Conditions
b). Scale …………………………………………………… ½ mark
NB: i). Penalise fully if any of the above conditions is not met
ii). Award for the scale even if the axes are in interchanged so long as the above conditions are met
c). Plotting ……………………………………………….. ½ mark i). For 5 or 6 points plotted correctly award 1 mark
ii). If 4 or 3 points are correctly plotted award ½ mark iii). For less than 3 points correctly plotted award 1 mark
Consider the rest of the plots (If any) as wrong plots
108 Chemistry Practical Study Pack 1989 – 2016
Award 1 mark
∆T
∆T ∆T
Volume of solution A (cm3) Volume of solution A (cm3)
Award 1 mark
∆T ∆T
|
Volume of solution A (cm3) b). Volume of solution A= Vcm
NB:
Volume of solution A (cm3)
1 mark
vi). Reject showing and reading of V from a wrong graph but accept in (c) below if need correct
correct ans.
NB; i). V of 30cm3 is unrealistic and unacceptable and hence penalize fully and consequently. Reject working in both d (i) and d (ii) below and award o mark in each case
ii). Penalise ½ mark for wrong units and another ½ mark if working not shown
= Ans (b); Ans (c) Or
Ans (c); Ans (b)
= 1: 1
NB: If ratio is not 1: 1 penalise ½ mark but accept the ratio in d (ii) if used correctly
Moles of acid used = Moles of NaOH Molarity of acid = 2 x Ans (c ) x 1000
1000 Ans (b)
= corr. Ans
OR
Conc of solution A = 2 x Ans (c)
Ans b
= Correct Ans
OR
MA VA = MB VB
MA = 2 x Ans
Ans(b)
= Corr. Ans
Conditions
NB: Penalise fully for any calculation noted beyond the expected ans.
| 2 | Observation | Inferences |
| a (i) | White ppt | B2+Ca2+, Ba2+, If all the 3 given 2 marks If only 2 given – 1 mark If only 1 given – ½ mark Note: for any contradictory mark out of 1 ½ ,penalize ½ mark for any contradictory |
| ii) | White ppt which dissolves in excess. reject residue Suspension Accept white solid | Pb2+, NB: Credit Pb2+ only if mention in (i) above, penalize fully for any contradiction |
| iii) | White PPt | –F contains SO 2–, Cl–, SO 2–, Cl–, or SO 2–, Cl–, 4 3 4 SO 2-, CO 2-, 4 ions given – 1 mark 3 3 3 or 2 ions given – ½ mark ions given – 0 mark Penalties |
| Penalise fully if candidate E contains the above ions – penalize ½ mark for contradictory ions | ||
| iv) | Yellow PPt | Pb2+ Penalise fully for any contradictory ions |
| bi) | Burns with a smoky/sooty flame/sooty flame Accept – yellow sooty | – C=C- / -C=C- Accept ; long chain hydrocarbon, carbon; hydrogen ratio Penalise fully for any contradictory functional group. |
| (ii) I | I pH is 1 or 3 accept red for ½ mk but reject inference given but reject inference given on its strength Reject PH range, penalize Fully for colour and correct PH NB: If a wrong colour | strongly acidic Reject – acidic given alone G – is a strong acid ignore – carboxylic acid |
| II | KMnO4 decolourised Or KMnO4 turns from Purple to colourless Reject KMnO4 turns colourless Solution turns colourless Solution decolourised Solution discolurised | – C = C- or – C = C- R – OH ½ Reject the groups in words – OH Penalise ½ mk for each contractor functional group |
| iii | Effervescence /bubbles /fizzing odourless gas odourless to differentiate between SO2 & CO2 Reject ; Hissing Odourless mentioned alone | CO 2- present in F (tied to part (a) (iii) 3 Ignore mention of acid ii). Penalise fully for contradiction iii).The inference is tied to effervescence bubbles and odourless |
NOVEMBER 2011 MARKSCHEME
Conditions (ii)
| 1 | 2 | 3 | |
| Final burette reading | 29.70 | 33.40 | 44.60 |
| Initial burette reading | 0.00 | 4.00 | 15.30 |
| Volume of solution A used (cm3) | 29.70 | 29.40 | 29.30 |
ii). Concentration in moles per litre of the dibasic acid in solution A Relative molecular mass of A is 126.
1.60 x 1000 1.60 1.60 x 1000 1.60 x 4
250 = 6.4 126 = 0.0127 126 126 126
6.4 moles in a litre = 0.051M
126 = 0.05 0.0127 x 1000
250
= 4 x 0.00127
= 0.051
1000
2 marks
= correct answer 1 mark
=correct answer
1 mark
Answer (iv) above x 1000 Answer (iv) above x 40 25
Correct answer Or Mb = Ans (iv) above x titre x 2 25
Correct answer
Or Ans (iv) x titre Mb x 25
= Correct answer
| 1st Conical flask | 2nd Conical Flask | |
| Final burette reading | 21.20 | 33.60 |
| Initial burette reading | 9.70 | 21.20 |
| Volume of solution A used (cm3) | 11.50 | 11.40 |
1000
= Correct ans
= Ans (ii) above x 2
= Correct ans
1 mark
1 mark
=Ans (iv) procedure II = Ans (iii) above
=Correct ans.
2 marks v). Given that I mole of salt B reacts with 2 moles of sodium hydroxide, calculate the;
2
Correct ans
1 mark
25
Ans I above x 40
= Correct ans
= 4.75
Ans in II above
= Correct answer > and > 140 penalise ½ mark for ans
1 mark
|
Gas that turns moist litmus paper NH + present (tied to red litmus Blue given off turning blue)
Condenses on the cooler parts of Solid D is hydrated /Solid D
The tube to form colourless liquid contains water of crystallisation Droplets (tied to idea of condensation)
White sublimate formed solid Sublimes to form white sublimate
A gas given off that turns moist blue Litmus paper red
A brown residue /solid formed
NB: Ignore mention of any other ions present
Yellow /brown solution formed Fe2+ oxidized to Fe3+ On addition of H2 O2 solution or
Brown ppt formed which is in soluble Fe3+ formed
In excess NaOH solution NB: ignore Accept Fe3+ present in Mention of initial colour of solution mixture of Fe2+ in
unless It contradictory solution
NB: Reject Fe3+ present /solid or solution D contains Fe3+
b). i). Observations Inferences
|
|
|
A white ppt formed SO 2-, SO 2- CO 2- present
NB: Penalise ½ mark for each contradictory ions for a max of ( 1 ½ mark)
ii). To the mixture obtained in (i) above, add about 5 cm3 of 2M nitric acid (V) acid Observations Inferences
|
Effervesces occurs /bubbles of SO 2- presents
Gas seen
The white ppt dissolves disappears NB: credit only if correctly inferred Correct inference tied to either observation or both
|
Penalise ½ mark for each contrition to a max of 1 mark Ignore SO 2 mentioned as absent
(VI) and warm the mixture
Observations Inferences
|
Acidified K2Cr2O7 solution SO 2- presents
Changes from orange to green NB: credit only if correctly inferred Correct inference tied to either observation or both
|
Penalise ½ mark for each contrition to a max of 1 mark Ignore SO 2 mentioned as absent
3 a). Observations inferences
Burns with a blue flame Reject C = C / C C absent
Saturated organic compound/organic Compound with low C: H ratio
Absence of unsaturated organic compound Ignore R-OH if mentioned
No of effervescence /No bubbles Absence of H+ or liquid is not acidic
/No of fizzing
Ignore does not dissolved Absence of R- COOH
No reaction Ignore H3O+ if mentioned Reject: No hissing on it’s own
green/solution changes from orange Reject; 1 – alcohol written in to green words 2-OH
Reject: soln turns green, NB: Penalise fully for any contradicting functional groups
NOVEMBER 2012 MARKSCHEME
1000
= Correct answer Conditions
Moles ratio moles of A : Moles of Na2S2O3 . 5H2O 1 : 6
Moles of A = 1
Moles of Na2SO3 SH2O Moles of A = ans a (ii) moles
6 = Correct answer ii). Concentration of A in moles per litre
25cm3 of A contains ans b(i) above 1000 cm3 of A contains
Ans b(i) x 1000
25
= correct answer OR
Ans b(i) x 40
= Correct answer
OR MA VA = 1 MB VB 6
MA = 0.05 x Average titre
6 x 25
= Correct answer
OR
Answer (b) (i) x 1000 = Correct answer
25
Conditions
d.p otherwise penalise ½ mark
for wrong units used
e). When formula is wrongly given in the formula method penalise fully NB: Penalise ½ mark for the answers in calculation a (i) and b (ii) if
candidate work beyond the expected answer
PROCEDURE II
Table 2 – 6 marks Distribution of marks
Complete table …………………………………………. (3 marks)
Compare the candidates 1st time reading to the S.V if within +2s award 1mk otherwise penalise fully
Note:
Award (1 mark) for time reading increasing continuously otherwise penalise fully
Graph
| Penalise fully if any of the above is not met Award for the scale even if the axis are inverted | ||
| C. | Plotting Conditions If 5 or 6 points are correctly plotted ………………. |
(1 mark) |
| If 3 or 4 points are correctly plotted ………… If less than 3 points …………………………… | (½ mark) (0 marks) |
Accept a straight line passing through at least 2 points correctly plotted and through the origin on extrapolation otherwise penalise fully
Calculations
i). For correct showing of i/t on the graph ½ mark ii). For stating the correct reading
e.g R = 0.003
iii). For t = 1/correct value
v). Correct value ½ (Must have units)
Conditions
Penalise
Penalise ½ mark for W.A if the answer is not within +2 units in the 1st d.p Correct units must be shown otherwise penalise ½ mark
| 2. | a).i). | I). | Observations A white precipitate | Inferences Presence of Pb2+, Ba2+, Ca2+ Only 2 – ½ mark Penalise ½ mark for each contradictory ion |
| II). | Observations No white ppt | Inferences Presence of Ba2+, Ca2+ Pb2+ absent ½ where the above Not mentioned penalise ½ mark for each contradictory ions | ||
| III). | Observations No white precipitate | Inferences Cl- absent Penalise fully for any contradictory ion Ignore mention of S0 2-, SO 2 of CO 2- as absent 4 3 3 |
ii). Observations
Effervescence/bubbled Solid contain NO3
Colourless gas/pungent choking (Tied to red litmus turning blue)
Smell
Red Litmus – blue Blue – remains blue
No effervescence/no bubbles Solid F is not acidic No fizzing OR
Absence of H+/H30+
Burns with a sooty flame Unsaturated /long chain /high C-H organic cpd organic cpds ratio present
Smoky flame or luminous Flame / Carbon –carbon double/triple Yellow flame bond written in words or aromatic cpds
ii). Observations Inferences
White suspensions Compound is slightly soluble Or Or
White solid remains undissolved Cpd is partially soluble
or
cpd is insoluble/cpd is nonpolar
Or Or
Accept colorless gas given off RCOOH or H+/H3O present
ii). Observations Inferences
Bromine water is not decolourised Carbon – carbon double/triple Or bond absent
Yellow/orange/brown/red Or
Remains persists Compound is saturated Bromine water remain yellow
NOVEMBER 2013 MARKSCHEME
Procedure I. Table 1.
table based on the rows used to plot the graph. However if the graph is not drawn then mark the first rows of the temperature reading.
v). If two or more graphs are plotted, mark the complete table based on the first row.
i). Whole number ii). 1 decimal point of either ‘0’ or ‘5’ Otherwise penalize fully
|
|
Compare the candidate temperature reading at t=0 with the school value (S.V) and award ½ mark. If the reading is within +2C of the S.V otherwise penalize fully
Trend …..
Awarded as follows;
Graph……
Distribution as follows.
Penalties
i). Area covered by plot should be atleast half of grid provided i.e 4 ½ by 3 ii). Scale interval should be consistent each axis
iii). All plots/points whether plotted or not (check the range of reading on the note. Penalise fully if any of the above conditions is not met
Conditions
Highest change in temperature, OT.
with/without showing…………. Provided 1st line passes through the plot at t=0 i.e limited
temperature.
ii). Award ½ mark for correct showing on a correctly DT value is wrong or missing iii). Award 0 max for DT stated from a wrong graph
Note: a). Ignore +ve or –ve sign on the DT value
b). Penalise ½ mark for wrong units otherwise ignore if omitted
Accept correct time reading from correctly extrapolated with or without showing for …. If wrong units of time are given penalize fully, otherwise ignore omission of units
Conditions
iv). Penalise ½ mark for wrong arithmetic on answer if it is outside + 200 joules or + 0.2 KJ iv). Ignore if no sign is given on the answer otherwise penalize ½ mark for positive sign (+)
Procedure II
Table 2 …………………….
Conditions
Penalties
i). Wrong arithmetric when determining the titre values ii). Inverted tables
Use of decimals …. Tied to 1st row and 2nd row only
Conditions
Compare the candidate’s titre values with the S.V and award marks as follows i). If at least one is within +0.1 of S.V award …
ii). If none is within + 0.1 but at least one is within + 0.2 of S.V award iii). If no value is within +0.2 award 0 marks
Note:
If there is;
Correct value and award accordingly.
Compare the candidate’s average titre with S.V i). If within +0.1 of S.V award
ii). If not within + 0.1, but within + 0.2 of S.V award….. ½ mark iii). If not within + 0.2 of S.V award 0 mark
Note;
|
b). i). Moles of MnO – = 0.02 x AV. Titre
1000
=Correct Ans.
Fe2+ : Mn04- = 5: 1
= 5 x Ans b(i) above
= Correct Ans.
25cm3
Or Ans b(ii) x 10
= Correct Ans
Penalties
i). Penalise ½ mark for wrong arithmetic if the error is outside +2 units in the 2nd d.p ii). Penalise ½ mark for no working shown but correct answer is written
/stated
Note:
Otherwise penalize rounding off to 1 dp or to a whole number
Penalties/Conditions
= Ans a(iii)
b(iii)
= correct ans.
Penalties/conditions
Note:
For continued working, mark only the 1st correct areas.
showing/without showing 1 mark II). from extrapolated graph – wrongly stated but shown on the
graph ½ mark
= 50 x 4.2 x DT
= Correct answer Joules J.j Or = 50 x 4.2 x D.J
1000
= Correct answer (Kilo joules K.J)
-Ignore formula for working DH. Given must be correct otherwise penalize ½ mark for wrong formula.
– Penalise ½ mark for wrong units or omission
-Ignore if no sign is given otherwise if no sign is given otherwise penalize ½ markf or (+) sign
1 ½ mark
| I | II | III | |
| Final burette reading | |||
| Initial burette reading | |||
| Volume of solution C used (cm3) |
a). 1 + 11 + 1
3 = ans
4 marks
1 mark
i).
| Observations | Inferences |
| -Colourless -Odourless gas produced -Gas extinguishes a burning splint -White residue or solid turns yellow when heated and turns white on cooling (1 mark) | -CO3 2- (Extinguishes burning splint) -Zn2+/ZnO formed (turned to white on cooling )
(1 mark) |
Award ½ mark upto a maximum of 1 mark
Penalise ½ mark for each contradictory low in each case Reject; ZnO present.
ii).
| Observations | Inferences |
| -Colourless -Odourless gas produced -Gas extinguishes a burning splint -White residue /solid turns yellow when heated and turns white on cooking (1 mark) | -CO3 2- present Penalize fully for any contradictory ion Zn2+ present (1 mark) |
Reject ; Hissing /Fizzing
iii).
| Observations | Inferences |
| -White ppt -soluble in excess (1 mark) | -Zn2+/Zno formed (turned to white ) (1 mark) |
Penalise fully for contradictory ions
b). i).
| Observations | Inferences |
| -White ppt -ignore if ppt is insoluble in excess (1 mark) | –Al3+, Pb2+, Mg2+ present Note (1 mark) |
ii).
iii).
Penalize fully for ppt dissolves
| Observations | Inferences |
| – No effervescence -No white ppt
(1 mark) | -CO 2-, SO 2- absent 3 3 (both ½ mark) -Al3+, Mg2+ present (1 mark) |
Accept : No ppt
½ mark – colourless solution formed
– Solution remains colourless
| Observations | Inferences |
| -White ppt formed -penalise fully if ppt dissolves (1 mark) | -Pb2+ ions absent penalized ½ mark for any contradictory ion SO42- present (1 mark) |
Penalise fully for any contradictions ions Accept if ions are written in words
| Observations | Inferences |
| – melts and burns with a sooty/luminous / yellow smoky flame (1 mark) | -‘C=C’/ C=C- -Organic compound with high C;L -Long chain organic compound – Unsaturated organic (1 mark) |
b). i).
Melts on its own for ½ mark Carbon – carbon dissolves C=C/C=C
Alkalines/alkynes
Long chain hydrocarbon
Note:
Penalise fully for any contradictory ion
| Observations | Inferences |
| -KMNO4/H+ is not decolouress colour of KMN04/H+ remains purple/purple colour of KMNO4/H+ persists or remains the same (1 mark) | -H+/H3O+ or 4 – COOH or carboxyli growing in words/solutions in acidic
1 mark |
Saturated organic compound present for ½ mark
| Observations | Inferences |
| -Effervescence /bubbles /fizzing (1 mark) | – H+/H3O+ or 4 –COOH or carboxyli growing in words /solution is acidic (1 mark) |
Accept : Colourless gas for ½ mark Reject : Hissing/fizzling
c).
| Observations | Inferences |
| -Dip the p H /universal paper into the solution from (b) above -match the colour obtained with the p H chart and not the p H= 1 or 2 (1mark) | -Solution is strongly acidic
(1 mark) |
Reject: p H range ( p H = 1 -2)
October – November 1989 Instructions to Schools.
This is information that enables the Head of the school and the teacher in charge of Chemistry to make adequate preparations for Chemistry Practical Examination.
In addition to the fittings and substances ordinarily contained in a chemical laboratory, the following should be provided.
Requirements per Candidate
Each candidate will require the following:
Access to
Preparations
October /November 1990. Requirements for Candidates
In addition to the fittings, substances and apparatus ordinarily found in a chemistry laboratory each candidate will require the following;
Access to:
Preparations
II). Take 10cm3 of the sulphuric acid solution prepared in (i) above and dilute it by adding distilled water to make it up to one litre of solution (S2).
October / November 1992 Requirements for Candidates
In addition to fittings and apparatus found in a chemistry laboratory, each candidate will require:
Access to:
Preparations
October /November 1993 Requirements for Candidates
In addition to the equipments, apparatus and chemicals found in an ordinary chemistry laboratory, each candidate will require the following;
Preparations
October / November 1994 Requirements for Candidates.
In addition to fittings and apparatus found in a chemistry laboratory, each candidate will require.
Preparations
October /November 1995
Requirements for Candidates
In addition to the equipment, apparatus and chemicals found in an ordinary chemistry laboratory, each candidate will require the following;
Access to:
Preparations
The 2.0M hydrochloric acid should be prepared accurately by adding 175cm3 of concentrated hydrochloric acid to about 700cm3 of distilled water. Shake well and make it up to the one litre
October /November 1996 Candidates requirements
In addition to the apparatus and chemicals found in an ordinary Chemistry laboratory, each candidate will require the following:
Access to
NB: Each of the above reagents should be supplied with a dropper.
Preparations
October / November 1997 Requirements to Candidates.
In addition to the fittings and apparatus found in a chemistry laboratory, each candidate will require. A
NB/ Each of the solutions in Bottle should be supplied with a dropper.
Preparations
October / November 1998 Requirements to Candidates.
In addition to the fittings and apparatus found in a chemistry laboratory, each candidate will require.
Means of labeling.
Access to:
Preparations
October / November 1999 Requirements to Candidates.
In addition to the fittings and apparatus found in a chemistry laboratory, each candidate will require the following.
Access to:
Preparations
October / November 2000 Requirements to Candidates
In addition to the fittings and apparatus found in a chemistry laboratory, each candidate will require.
Access to
Preparations
litre of solution.
October / November 2001 Requirements to Candidates.
In addition to the fittings and apparatus found in a chemistry laboratory, each candidate will require.
Access to.
Preparations.
accurately) in about 500cm3 of distilled water and diluting to one litre of solution.
October / November 2002 Requirements to Candidates.
In addition to the fittings and apparatus found in a chemistry laboratory, each candidate will require. A
Preparations
of distilled water and diluting to one litre of solution. (This solution should be prepared one day before the day of examination, stored in Stoppard container and supplied on the morning of the examination).
October / November 2003 Requirements to Candidates.
In addition to the fittings and apparatus found in a chemistry laboratory, each candidate will require.
A.
These solutions should be supplied with droppers.
Preparations
NB/ The quantities in the above preparations will depend on the number of candidates in a centre.
October / November 2004 Requirements to Candidates.
In addition to the fittings and apparatus found in a chemistry laboratory, each candidate will require.
A.
Preparations
to one litre of solution.
October / November 2005 Requirements to Candidates.
In addition to the fittings and apparatus found in a chemistry laboratory, each candidate will require.
A.
Preparations
1 Solution K is prepared by dissolving 37.32g of sodium hydroxide pellets in about 600cm3 of distilled water and diluting to one litre of solution.
diluting to one litre of solution.
October / November 2006 Requirements to Candidates.
In addition to the fittings and apparatus found in a chemistry laboratory, each candidate will require
Preparations
October / November 2007 Requirements to Candidates.
In addition to the fittings and apparatus found in a chemistry laboratory, each candidate will require.
Access to:
Preparations
NB/ The test-tubes provided should have a capacity of at least 15cm3.
October / November 2008
Requirements to candidates.
In addition to the fittings and apparatus found in a chemistry laboratory, each candidate will require.
Access to.
Preparations
(VI) in about 600cm3 of 2M sulphuric acid and diluting to one litre of solution.
October / November 2009 Requirements to Candidates.
In addition to the fittings and apparatus found in a chemistry laboratory, each candidate will require.
Access to:
Preparations
(VI) in about 400cm3 of 2M H2SO4 acid and making to one litre of solution using distilled water and labelled acidified potassium dichromate (VI) solution.
October /November 2010 Candidates Requirements
In addition to the apparatus and fittings found in a chemistry laboratory, each candidate will require the following;
Access to
Preparations
October /November 2011
In addition to the apparatus and fittings found in a chemistry laboratory, each candidate will require the following;
A.
In addition to the apparatus and reagents found in a chemistry laboratory, each candidate will require the following:
Access to:
NB: Solids A, C, D, E and F will be supplied by the Kenya National Examination Council
October /November 2013
In addition to the apparatus and reagents found in a chemistry laboratory, each candidate will require the following:
Preparations
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