SECTION A

1. (a) Define the relative atomic mass (Ar) of an element.

______________________________________________________________

______________________________________________________________(1 mark)

(b) The relative atomic masses of elements P, Q, and R are 24, 36 and 48 respectively.i) How many atoms of element Q have the same mass as one atom of

element R?

__________________________________________________________(1 mark)

ii)

How many times are two atoms of element P and for four atoms of element Q heavier than one atom of element R?

__________________________________________________________(1 mark)

(c) Complete the table below.[Relative atomic mass of H = 1, C = 12, O = 16 and S = 32; Avogadro constant = 6.02×1023 mol−1 and 1 mol of gas occupies 22.4 dm3 at STP]

Formula

Mass (g)

Number of moles

Volume of gas at STP (dm3)

Number of atoms

CO2 1.76

SO3 12.00

H2 6.72

(d) Cocaine, C17 H21 O4 N is a drug.[Relative atomic mass of H = 1, C = 12, N = 14 and O = 16; Avogadro constant = 6.02×1023 mol−1]i) Calculate the mass of 2 moles of the drug.

(1 mark)

ii)

Calculate the number of molecules in 4.242 g of cocaine.

(1 mark)

2. Diagram below shows the set-up of apparatus of an experiment to determine the empirical formula of magnesium oxide.

Results:Mass of crucible + lid = 18.30 gMass of crucible + magnesium ribbon = 19.20 gMass of crucible + magnesium oxide = 19.8 g

(a) Suggest a method to remove the layer of magnesium oxide on the surface of the magnesium ribbon before heating.

______________________________________________________________(1 mark)

(b) Give a reason why the crucible lid cannot be left open during the experiment.

______________________________________________________________

______________________________________________________________(1 mark)

(c) Based on the results above,i) Determine the empirical formula of magnesium oxide.

[ Relative atomic mass: O = 16; Mg = 24]

(3 marks)

ii Write the empirical formula for the reaction in the experiment.

Lid

CrucibleMagnesium ribbon

Pipe-claytriangle

) __________________________________________________________(1 mark)

(d) A student carried out a laboratory activity to determine the empirical formula of the oxide of metal X using the apparatus below.

i) Suggest a metal for X that will use the above method to determine the empirical formulae.

__________________________________________________________(1 mark)

ii)

What are the safety precaution steps that should be taken during the experiment?

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________(3 marks)

3. Hydrocarbon Z contains 81.8% carbon and 18.2% hydrogen by mass. 13.2 g of hydrocarbon Z occupies a volume of 7.2 dm3 at room temperature and pressure.[Relative atomic mass of H = 1, C = 12 and O = 16; 1 mol of gas occupies a volume of 24 dm3 at room temperature and pressure; Avogadro constant =

6.02×1023 mol−1]

(a) Determine the empirical formula of hydrocarbon Z.

Burning of excess hydrogen gas

Porcelain dish

Heat

Combustion tube

Retord stand

Oxide of metal X

(3 marks)

(b) Calculate the relative molecular mass of hydrocarbon Z.

(3 marks)

(c) What is meant by molecular formula?

______________________________________________________________

______________________________________________________________(1 mark)

(d) Determine the molecular formula of hydrocarbon Z.

______________________________________________________________(1 mark)

(e) The combustion of hydrocarbon Z in air produces carbon dioxide and water. Write a balanced chemical equation for the reaction.

______________________________________________________________(1 mark)

(f) If 3.52g of hydrocarbon Z is burnt, calculatei) the mass of water formed.

(1 mark)

ii)

the volume of carbon dioxide produced at room temperature.

(1 mark)

4. When lead(II) nitrate is heated, it decomposes to become lead(II) oxide, nitrogen dioxide and oxygen.

(a) Write a balanced chemical equation for the decomposition of lead(II) nitrate upon heating.

______________________________________________________________(2 mark)

(b) If 1.986 g of lead(II) nitrate decomposes, calculatei) the volume of oxygen gas released at STP.

[Relative atomic mass of C = 12, N = 14 and Pb = 207; 1 mol of gas occupies 22.4 dm3 at STP]

(3 marks)

ii)

the mass of lead(II) oxide formed.

(2 marks)

(c) Lead(II) carbonate reacts with nitric acid (HN O3) to form lead(II) nitrate carbon dioxide and water.i) Write a balanced chemical equation for this reaction.

__________________________________________________________(2 marks)

ii)

the mass of lead(II) nitrate produced when 21.36 g of lead(II) carbonate reacts with excess acid.[Relative atomic mass of C = 12, N = 14, O = 16 and Pb = 207]

(3 marks)

SECTION B

5. (a) Using two suitable examples, give the meaning of one mole of a substance.(3 marks)

(b) i) Using two suitable examples, give the meaning of molar volume of agas. (3 marks)

ii)

What is the molar volume of a gas at STP and room conditions

respectively? (2 marks)

(c) Determine the relative molecular mass or relative formula mass of the following compounds.

Benzene, C6 H6

Copper(II) nitrate, Cu(N O3)2

Carboxylic acid, CnH2n+1COOH

[Relative atomic mass of H = 1, C = 12, N = 14, O = 16 and Cu = 64]

(3 marks)

(d) Calculatei) the molar mass of urea, CO(N H2¿2. (1 mark)

ii)

the volume of 8.5 g of ammonia gas at STP. (3 marks)

[Relative atomic mass of H = 1, C = 12, N = 14 and O = 16; 1 mol of gasoccupies 22.4 dm3 at STP]

6. (a) The following are formulae of two chemical compounds.

PbO2 CuC l2

i) Based on the formulae given above, state the oxidation number for

lead and copper. (2 marks)

ii) Name both the compounds based on the IUPAC nomenclature system.(2 marks)

iiii) Explain the difference between the names of the two compounds based on the IUPAC nomenclature system. (2 marks)

(b) The information below is about a compound X.

Carbon = 82.76% Hydrogen = 17.24% Relative molecular mass = 58 Relative atomic mass: H, 1; C, 12

i) Define empirical formula and molecular formula. (2 marks)

ii) Determine the empirical formula of compound X. (2 marks)

iii) Determine the molecular formula of compound X. (3 marks)

iv) Compound X burns in excess oxygen to produce carbon dioxide and water. Write a balanced chemical equation to represent the reaction.

(2 marks)

(c) The diagram below shows a reaction. Copper solid is formed after zinc plate is put into copper(II) sulphate solution.

i) Write a balanced chemical equation to represent the reaction.(2 marks)

ii) Calculate the mass of copper solid formed if the mass of zinc used is 4.05 g in excess copper(II) sulphate solution.[Relative atomic mass: Cu, 64; Zn, 65] (2 marks)

Zinc

Copper(II) sulphate solution

SECTION C

7. (a) Describe a laboratory activity to determine the empirical formula of aluminium oxide. Include observation and inferences. State also the precautionary steps to be taken. (16 marks)

(b) The following are two formulae for one compound.

C6H 12O6 CH2O

Using the above compound, explain the difference between empirical formula and molecular formula. (4 marks)

8. (a) When zinc nitrate is heated, it decomposes to form zinc oxide, nitrogen dioxide and oxygen.

i) Write a balanced chemical equation for the decomposition of zinc nitrate upon heating. (2 marks)

ii) State three qualitative aspects that can be obtained from the chemical equation. (3 marks)

iii) State the observations for nitrogen dioxide and oxygen gas respectively. (5 marks)

(b) If 37.8 g of zinc nitrate decomposes, calculate

i) the volume of nitrogen dioxide gas evolved at room temperature and pressure. (3 marks)

ii) the mass of zinc oxide formed. (2 marks)

[Relative atomic mass of N = 14, Cl = 35.5, O = 16 and Zn = 65]

(c) Zinc carbonate reacts with hydrochloric acid (HCl) to form zinc chloride, carbon dioxide and water.

i) Write a balanced chemical equation for this reaction. (2 marks)

ii) Calculate the mass of zinc carbonate that reacts with the excess acid to produce 10.88 g of zinc chloride.[Relative atomic mass of N = 14, Cl = 35.5, O = 16 and Zn = 65]

(3 marks)