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Chapter 3 Chemical Formulae and Equations

Paper 1Answer all the questions.

1 The number of molecules in one mole of a gas is x. What is the number molecules in 8 g of oxygen gas?

[Relative atomic mass: O, 16] A 8x B 0.25x C x D 0.5x 2 How many water molecules are contained in 4.5 g of water?

[Relative atomic mass: H, I; O,16] A 6 x 1023

B 4 x 1023 C 0.25 x 6 x 1023

D 1.5 x 6 x 1023

3 One mole of methane,CH

4 and one of carbon dioxide,CO

2 have equal

[Relative atomic mass: H, I; C,12; O,16] I volume at the same temperature and pressure II number of atoms III relative molecular mass IV number of molecules A IV only B I and IV only C II and IV only D I, II and IV only 4 What is the mass of one mole of chlorine molecules? [Relative atomic mass: CI, 35.5] A 35.5 g B 71.0 g C 6 x 1023 g D 24 g 5 How many moles of oxygen, O

2, are needed for the complete combustion of one mole of

propane, C3H

8?

A 3 B 5 C 8 D 10 6 What is the maximum mass of aluminium which can be obtained from 102 g of aluminium

oxide, AI2O

3?

[Relative atomic mass: O,16; Al, 27] A 27 g B 51 g C 54 g D 108 g

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7 The main ore of zinc is zinc blende, ZnS (Realative molecular mass: 97). When this ore is heated in air, the reaction is represented by the following equation.

2ZnS + 3O

2 → 2ZnO + 2SO

2

What is the volume of oxygen at room temperature and pressure would be needed to react

completely with 97 g of ZnS? [Relative atomic mass: O,16; S, 32; Zn, 65] A 3 dm3

B 3 x 24 dm3

2 C 3 x 24 dm3

D 3 x 24 x 32 dm3

8 The empirical formula of a liquid compound is known as C

2H

4O. What other information is

needed to work out its molecular formula? A The percentage composition of the compound B The relative molecular mass of the compound C The volume of the compound D The boiling point of the compound 9 How many moles of hydrogen atoms are there in 0.5 mole of glucose, C

6H

12O

6?

A 6 B 3 C 1.5 D 0.5 10 When hot iron gas fi llings are heated in a stream of dry gas, X

2, the compound formed

contains 34.5% by mass of iron. What is the empirical formula of the compound? [Relative atomic mass: X, 35.5; Fe, 56]

A FeX B FeX

2

C FeX3

D Fe3X

11 Methane reacts with steam according to the equation:

CH4(g) + H

2O(g) → CO(g) + 3H

2(g)

What is the volume of hydrogen obtained (at room temperature and pressure) when 16 g of methane is reacted with excess steam?[Relative atomic mass: C,12;O,16]

A 24 dm3

B 48 dm3

C 60 dm3

D 72 dm3

12 Which of the following compounds has the similar empirical formula as ethene, C

2H

4?

A C6H

12

B C6H

6

C CH4

D C5H

12

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13 Potassium reacts with oxygen gas to form potassium oxide. Which of the following is a balanced chemical equation for the reaction?

A K(s) + O(g) → KO(s) B 2K(s) + O(g) → K

2O(s)

C K(s) + O2(g) → KO

2(s)

D 4K(s) + O2(g) → 2K

2O(s)

14 Which of the following ions corresponds to the charges it carries?

Ion Charges

A P –3 B S +2 C NO

3 +1

D Li –1 15 How many atoms are there in 1 mole of chlorine and 1 mole of argon?

1 mole of chlorine 1 mole of argon

A 6 x 1023 atoms 6 x 1023 atoms B 2 x 6 x 1023 atoms 2 x 6 x 1023 atoms C 2 x 6 x 1023 atoms 6 x 1023 atoms D 6 x 1023 atoms 2 x 6 x 1023 atoms 16 Which of the following ions are cations? I Sulphate ions II Calcium ions III Ammonium ions IV Phosphate ions A I and II only B II and III only C III and IV only D I, II and III only

17 The following are the characteristics of an ion of element Q.• Consists of two negative charges•• Consists of chromium and oxygen atoms• Ratio of chromium to oxygen atoms is 2:7

From the information above, it can be deduced that the ionic formula of the ion Q is A CrO2-

B Cr2O

72-

C CrO4

2-

D Cr2O

3

18 How many moles of ions are there in 1 mole of iron(III) oxide, Fe2O

3?

A 2 B 3 C 5 D 6

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19 Ammonium phosphate is commonly used as a chemical fertiliser. What is the chemical formula of ammonia phosphate?

A NH3PO

4

B (NH4)

2PO

4

C NH4(PO

4)

3

D (NH4)

3PO

4

20 The fi gure below shows dry hydrogen gas is passed over a powdered oxide of X.

A liquid N is collected. The liquid N would A neutralise sodium hydroxide B turn white anhydrous copper(II) sulphate blue C has pH value greater than 7 D be a blue liquid

dry hydrogenpowdered X oxide

liquid N

cold water

heat