CHEMISTRY FORM 3 END TERM EXAMS PLUS ANSWERS

ULTIMATE ACHIEVERS ACADEMY

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END OF TERM  EXAMINATION 

FORM THREE

CHEMISTRY

2 HOURS

Instructions to candidates:

1. Answer all questions in both section A and B.
2. All working must be clearly shown and, in the spaces provided.

FOR EXAMINER’S USE ONLY

Section	Maximum Score	Candidate’s Score
A	40
B	40
Grand Score	80

 

SECTION A                                                                                                               40MARKS

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1. Distinguish between an element and a compound. (2 Mks)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

2. A compound has an empirical formula of C₂H₅ Given it has a R.M.M. of 90, determine its molecular formulae. (C=12, H=1, O=16)                                                 (2 Mks)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

3. Identify the particles responsible for electrical conductivity in each of the following. (3 Mks)
4. Molten sodium chloride

…………………………………………………………………………………………………

1. Zinc metal

…………………………………………………………………………………………………

1. Graphite

…………………………………………………………………………………………………………

4. The diagram below shows a set up used to investigate one of the conditions necessary for rusting.

 

1. Identify the conditions being investigated in the experiment. (1 Mk)

………………………………………………………………………………………………

1. State whether rusting occurred or Not. (1 Mk)

………………………………………………………………………………………………

1. Explain why rusting occurs faster near factories that emit gases such as CO₂, NO₂ and SO₂ into the atmosphere.                                                       (2 Mks)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

5. Explain why a reaction occurs between copper (ii) oxide and magnesium powder, but no reaction occurs between magnesium oxide and copper powder.                                           (2 Mks)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

6. The set-up below shows one of the methods used to separate a mixture of liquids P and Q

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1. State two properties of the liquids P and Q that make it possible to separate using the above method.                                     (2 Mks)

………………………………………………………………………………………………………………………………………………………………………………………………

1. Name any other two methods that can be used to separate the mixture of liquids p and Q.

(2 mks)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

7. The diagram below shows arrangement of particles in the three state of matter in no particular order.

 

 

 

 

 

 

 

1. Which of the diagrams I, II and III represents;
2. Matter in the solid state. (1 Mks)

………………………………………………………………………………………

1. Matter in the gaseous state. (1 Mk)

………………………………………………………………………………………………

• State in which matter has the highest kinetic energy. (1 Mk)

………………………………………………………………………………………………

8. The ratio of the rates if diffusion of gas X and gas y is 3:8. Given that 200 cm³of gas X diffuse through a porous plug in 75 seconds. How long would it take 160 cm³ of gas Y to diffuse under the same conditions?                                           (3 Mks)

 

 

 

 

 

8. Describe how you can prepare a dry sample of barium sulphate starting with Barium nitrate crystals. (3 Mks)

……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

9. Sodium carbonate can be obtained on large scale by manufacturing through the Solvay process.
10. Name two raw materials for this process. (2 Mks)

……………………………………………………………………………………………………………………………………………………………………………………………………

1. Identify any other method that can be used to obtain sodium carbonate on large scale.

(1 Mk)

…………………………………………………………………………………………………

• State one use of sodium carbonate. (1 Mk)

…………………………………………………………………………………………………

10. Molten lead (ii) bromide was electrolyzed using carbon electrodes.
11. Name any other substance that can suitably be used as electrodes in place of carbon. (1 Mk)

…………………………………………………………………………………………………

1. Name the product formed at the cathode. (1 Mk)

…………………………………………………………………………………………………

1. Write the ionic equation of the reaction that occurred at the cathode. (1 Mk)

…………………………………………………………………………………………………

11. The diagram below shows parts of a set-up to prepare and collect dry hydrogen gas.

 

 

 

 

1. Identify reagent N and drying agent K. (2 Mks)

……………………………………………………………………………………………………………………………………………………………………………………………………………………

1. Complete the diagram to show how the dry hydrogen gas is collected.                                     (2 Mks)

 

……………………………………………………………………………………………………………………………………………………………………………………………………………………

12. Using universal indicator, describe how you can determine the PH value of a given solution.

(2 Mks)

……………………………………………………………………………………………………………………………………………………………………………………………………………………

1. State one advantage of universal indicator over other commercial indicators. (1 Mk)

……………………………………………………………………………………………………………………………………………………………………………………………………………………

 

SECTION B

13. The grid below shows a section of the periodic table, the letters are not the actual chemical symbols.

 

 

1. Name the family into which element Q belongs to (1 Mk)

…………………………………………………………………………………………………

1. Element E can be placed in group I or group VII. Explain why (2 Mks)

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

 

1. What Name is given to the elements found in the shaded region W. (1 Mk)

 

…………………………………………………………………………………………………………

1. Which letter represents element with the highest melting point in group II. Give reasons

(2 Mks)

……………………………………………………………………………………………………………………………………………………………………………………………………………………

1. Write the chemical formulae of the;
2. Sulphate of L (1 Mk)

…………………………………………………………………………………………………………

1. Nitrate of R (1 Mk)

…………………………………………………………………………………………………………

1. How does the following compare? Explain your answer
2. Reactivity of J and N. (2 Mks)

……………………………………………………………………………………………………………………………………………………………………………………………………………………

1. Boilling point of the oxides of M and T.                         (2 Mks)

……………………………………………………………………………………………………………………………………………………………………………………………………………………

14. In an experiment, 80 cm³ of 0.75 M hydrochloride acid were reacted with excess zinc carbonate to form solution W, Liquid R and gas T.
15. Identify solution W and gas T. (2 Mks)

……………………………………………………………………………………………………………………………………………………………………………………………………………………

1. Write a chemical equation of the reaction that occurred. (1 Mk)

…………………………………………………………………………………………………………

1. Calculate the;
2. Number of moles of hydrochloric acid that reacted with the zinc carbonate. ( 2 Mks)

 

 

1. Number of moles of the Zinc carbonate that reacted with the acid (2 Mks)

 

 

• Mass of the Zinc carbonate that reacted with the acid. (Zn = 65, C= 12, O= 16)

(2 Mks)

 

 

 

1. Volume of gas T evolved at r.t.p. (1 Mole of gas at r.t.p. = 24 litres) (2 Mks)

 

 

15. (a). Name the following hydrocarbons                                           (3Mks)
16. CH₃CH₂CH₂CH₂CH_{3 ______________________________________}

 

 

1. CH₃CHCHCHCH_{2 ________________________________________}

 

Br        CH₃                               Br

• H –   C    –    C    –    C    =    C   –    C   –   H

 

 

H               CH₃                       H

 

1. The diagram below shows some reactions involving hydrocarbons.

 

 

 

 

 

 

1. Identify the following (5 Mks)

I – substance L

…………………………………………………………………………………………………………

II – Substance M

…………………………………………………………………………………………………………

III – Substance Q

…………………………………………………………………………………………………………

IV – Process P

…………………………………………………………………………………………………………

V – Process N

…………………………………………………………………………………………………………

1. Name two substances that can be used as catalysts during process W. (2 Mks)

……………………………………………………………………………………………………………………………………………………………………………………………………………………

16. Nitrogen (iv) oxide is one of the oxides of nitrogen.
17. Name the other two oxides of nitrogen (2 Mks)

……………………………………………………………………………………………………………………………………………………………………………………………………………………

 

1. Which of the oxides you have named in a(i) above relights a glowing splint. (1 Mk)

 

……………………………………………………………………………………………………………………………………………………………………………………………………………………

1. Ammonia is a compound of nitrogen that can be obtained industrially by the Haber process;
2. Other than nitrogen, name the other raw material for this process. (1 Mk)

…………………………………………………………………………………………………………

1. Write a chemical equation of the reaction that occurs in the catalytic chamber to produce Ammonia. (1 Mk)

……………………………………………………………………………………………………………………………………………………………………………………………………………………

• State one use of ammonia (1 Mk)

……………………………………………………………………………………………………………………………………………………………………………………………………………………

1. When burning magnesium is lowered into a gas jar containing air magnesium oxide is one of the products formed. Name the other product that can possibly be formed. (1 mk)

……………………………………………………………………………………………………………………………………………………………………………………………………………………

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FORM 3 CHEMISTRY

END TERM 1 2019

MARKING SCHEME

MARKING SCHEME

1. An element is a pure substance which you can be split into simpler substance by chemical means while   a compound is a pure substance made up of two or more elements chemically combined

(Both must be correct to score)

2. (C₂H₅O)n = 90

(12×12+1×5+16)n = 90

(45)n/45 =90/45

n=2

M.F – C₄H₁₀O₂

3. mobile ions
4. delocalized electrons
5. delocalized electrons

 

4. water vapour/ moisture
5. Rusting will not take place
6. Gases emitted react with water vapour to form acid rain there by accelerating rusting.

 

5. Magnesium powder is more reactive than copper therefore it is able to remove combined oxygen from copper while copper is less reactive than magnesium hence cannot remove combined oxygen from magnesium oxide.

 

6. – The liquids are immiscible

• They have different densities

1. – Decantation

–  use of separating funnel

 

7. i) II
8. ii) I

iii) I

1. 200 cm³ = 75 sec

169 cm³= ?

160 x 75  = 60 sec

200

RX/RY = Time Y/Time x

3/8 = 60/ Time x

Time x= 60×8

3

=160 Sec

 

 

• Add distilled water to Barium nitrate and stir.
• Filter the mixture
• Add Na2SO4 to the filtrate (Any soluble sulphate)
• Filter to obtain insoluble Barium Sulphate
• Rinse with distilled water
• Dry between filter papers

(Each step ½ x 6= 3 Mark)

9. 1. Ammonia, Brine, Calcium carbonate, coke (Any two correct)
   2. Extraction from trona
   3. Used in softening hard water

In glass making

(Any one correct)

10. 1. Platinum electrode
    2. Lead metal
    3. Pb²⁺ + 2e                                 Pb_(s)
11. 1. Reagent N – Dilute Hydrochloric acid

Drying agent K – Concentrated sulphuric (vi) acid

 

 

 

 

12. S
    1. – add 3 drops of universal indicator to the solution in the test tube.

–  match the resulting colour of the mixture against the colors on the PH chart

– The PH value of the matching colour of the PH chart gives the PH value of the solution.

1. Shows strength of acids and bases

 

Section B – 40 marks

 

13. 1. Alkali metals
    2. In group I it reacts by losing one electron while in group (VII) it can react by gaining one electron.
    3. Transition metals
    4. K – It has shorter/ smaller atomic radius hence stronger effective force of attraction between the delocalized electron and the positive nuclei hence stronger metallic bond.
    5. L2(SO4)3 / AL2(SO4)3
14. D
    1. Solution W – Zinc Chloride

Gas  T- carbon iv oxide

1. ZnCO_3(s) + 2HCl_(aq) ZnCl₂ + H₂O_(l) +CO_2(g)

 

1. 0.75 moles 1000 cm³

?                      80cm³

0.75 x80

1000

= 0.06 moles

1. Mole ratio 1          :           2

?                      0.06

0.06 X 1

2

=0.03 moles

iii. 1 mole of ZnCO₃                 125g

0.03 moles                    ?

125 X 0.03

1

= 3.75g

1. Mole ratio 2HCl : 1CO₂

                                                            Moles of HCl = 0.06

Moles of CO₂ =0.06

2

= 0.03

1 Mole of r.t.p.             24 l

0.03 mole                ?

0.03 X 24

1

= 0.72 l

15. 1
    1. (i) Pentane

(ii) Pent-1,2,3- tri-ene

(iii)1,5- dibromo, 4,4-dimethylpent – 2 – yne

1. (i) I Ethane

II Sodium Propanoate

III Bromoethane

IV Polymerization

V Dehydration

(ii) Nickel and palladium catalyst

 

16. (a) (i)         Nitrogen (i) oxide / N₂O

Nitrogen (ii) oxide / NO

(ii)        Nitrogen (i) oxide

(b)        (i)         Hydrogen

(ii)        N_2(g) + 3H_2(g)                   2NH_3(g) + heat

(iii)       Manufacture of nitrogenous fertilizer

Removes greasy stains

(c) Magnesium nitride / Mg₃N₂