QB_metal_ans

Question Bank Topic 3

Metals

Name: ___________________________ Class: ____________ Class No: __________

Mark: ___________ Date:______________

Multiple choice questions

Unit 9

9.1: Metals in our lives

9.2: Uses of metals and their properties

9.3: Metals in the Earth’s crust

(CDC guide: Occurrence of metals in nature and their uses in daily life)

1 The most abundant metal in the Earth’s crust is

A iron.

B aluminium.

C mercury.

D copper.

B2 Which of the following metals is used in making jewellery?

A Gold

B Tin

C Aluminium

D Lead

A

3 Which of the following metals is used to make overhead power cables?

A Copper

B Iron

C Aluminium

D Zinc

C4 Which of the following combinations concerning the use of metal is correct?

Metal Use

A Copper Electrical wires

B Iron Cooking foil

C Lead Food cans

D Magnesium Water pipes

A5 Which of the following combinations concerning the use of metal is INCORRECT?

Metal Use

A Aluminium Window frames

B Silver Jewellery

C Magnesium Railings

D Tungsten Light bulb filaments

C6 Which of the following objects is least likely to contain titanium?

A Joint replacement part

B Spectacles

C Watch case

D Water tap

D7 Which of the following combinations concerning the use of metal is correct?

Metal Use

A Lithium Making dry cells

B Copper Making fuses in electric plugs

C Titanium Making light bulb filaments

D Zinc Making cans for canned foods

A8 Which of the following metals are suitable for making cooking utensils?

(1) Aluminium

(2) Copper

(3) Lead

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

A9 Brass, an alloy of copper and zinc, is commonly used for making ornaments because

(1) it has an attractive appearance.

(2) it can resist corrosion.

(3) its melting point is lower than copper.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

A10 Titanium is used in making supersonic aircraft bodies. Which of the following are reasons of

using titanium for making aircraft bodies?

(1) It is light but strong.

(2) It is cheap.

(3) It is very corrosion resistant.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

B11 Common uses of aluminium include

(1) making window frames.

(2) making soft drink cans.

(3) making electronic components.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

A12 Which of the following statements concerning iron are correct?

(1) It is the second most abundant metal in the Earth’s crust.

(2) It can be used to make drain covers.

(3) It is corrosion resistant.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

A13 Aluminium is used to make cooking foil because

(1) it is very malleable.

(2) it resists corrosion.

(3) it is a good conductor of heat.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D14 Copper is NOT suitable for making overhead cables because

(1) its density is high.

(2) its price is high.

(3) its electrical conductivity is low.

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

A

9.4: Occurrence of metals in nature and their extraction methods

(CDC guide: Obtaining metals by heating metal oxides or by heating metal

oxides with carbon & Extraction of metals by electrolysis)

1 The main ore of iron is

A bauxite.

B carnallite.

C cinnabar.

D haematite.

D2 Which ore contains aluminium?

A Bauxite

B Carnallite

C Haematite

D Galena

A3 Which of the following methods is most suitable for extracting sodium from sodium chloride?

A Heating sodium chloride with carbon

B Heating sodium chloride in air

C Electrolysis of molten sodium chloride

D Electrolysis of sodium chloride solution

C4 Aluminium is commonly extracted by electrolysis of its molten

A carbonate.

B sulphate.

C oxide.

D sulphide.

C5 Which of the following metals can be extracted from its oxide by heating in air?

A Lead

B Mercury

C Zinc

D Iron

B6 Which of the following metal oxides CANNOT be reduced to form metal when heated with

carbon?

A Copper(II) oxide

B Iron(III) oxide

C Zinc oxide

D Magnesium oxide

D7 Which of the following methods can be used to extract iron from iron(III) oxide?

A Heating iron(III) oxide in air

B Heating iron(III) oxide with carbon at about 600 oC

C Heating iron(III) oxide with carbon at about 1000 oC

D Mixing iron(III) oxide with carbon monoxide at room temperature

C8 Which of the following compounds does NOT undergo a chemical change upon heating?

A Iron(II) sulphide

B Mercury(II) sulphide

C Silver oxide

D Sodium oxide

D9 Carbon is used as a reducing agent in the extraction of iron from its ore because

A carbon is cheap.

B carbon is a non-metal while iron is a metal.

C carbon is a good conductor of electricity.

D pure carbon can be obtained readily.

A10 Which of the following groups of metals are extracted by electrolysis?

A K, Mg and Zn

B Na, Ca and Al

C Al, Ca and Fe

D Fe, Ag and Cu

B11 A small amount of silver oxide is heated in a boiling tube. Which of the following graphs

represents the correct plot?

ADirections: Questions 12 and 13 refer to the following electrolytic cell used to obtain

aluminium metal from aluminium oxide.

12 From which element are the electrodes made?

A Graphite

B Iron

C Sulphur

D Zinc

A13 The positive electrodes are replaced frequently because they react with

A aluminium.

B aluminium oxide.

C cryolite.

D oxygen.

D14 The diagram shows a method for changing a metal oxide into a metal.

Which oxide below can be changed into a metal by this method?

A Calcium oxide

B Copper(II) oxide

C Magnesium oxide

D Potassium oxide

BDirections: Questions 15 and 16 refer to the diagram which shows substances used in a blast

furnace to produce iron.

15 What is substance X?

A Chromium

B Coke

C Calcium oxide

D Sulphur

B16 Which of the following substances would react with the iron(III) oxide in the furnace to

produce iron?

A Carbon dioxide

B Carbon monoxide

C Hot air

D Oxygen

B17 Which of the following metals can be found free in nature?

(1) Lead

(2) Gold

(3) Silver

(4) Mercury

A (2) and (3) only

B (1), (2) and (3) only

C (1), (2) and (4) only

D (1), (3) and (4) only

A

18 Which of the following metals can be extracted from their oxides by heating with coke?

(1) Calcium

(2) Iron

(3) Lead

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

C19 Which of the following metal oxides can be reduced when heated with carbon at 600 oC?

(1) Lead(II) oxide

(2) Copper(II) oxide

(3) Zinc oxide

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

A20 Which of the following statements are correct?

(1) Extraction of metals by electrolysis is more expensive than by reduction with carbon.

(2) When lead(II) sulphide is heated in air, lead(II) oxide and sulphur dioxide will be

obtained.

(3) Carbon monoxide can be used to reduce iron(III) oxide.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D21 In which of the following processes would a metal be produced?

(1) Heating mercury(II) sulphide in air.

(2) Heating magnesite with carbon.

(3) Controlled heating of copper pyrite in air.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

B22 In which of the following experiments would a gas be produced?

(1) Reacting iron(III) oxide with carbon monoxide

(2) Heating limestone strongly

(3) Heating lead(II) sulphide in air

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D

9.5: Discovery of metals and the ease of extraction

(CDC guide: Relation of the discovery of metals with the ease of extraction of

metals and the availability of raw materials)

1 Three metals, X, Y and Z were discovered in A.D.1807, B.C. 3500 and A.D. 1746 respectively.

The order of increasing ease of extraction is probably

A X, Y, Z.

B X, Z, Y.

C Y, X, Z.

D Y, Z, X.

B2 Ancient people discovered copper, but not aluminium because aluminium

A is very rare.

B is difficult to extract.

C is light.

D is found very deep in the Earth’s crust.

B3 The year of discovery of a metal is closely related to

(1) the ease of extraction from its ore.

(2) the thermal stability of its ore.

(3) its melting point.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

A4 The price of a metal depends mainly on

(1) its abundance in the Earth's crust.

(2) the extraction method used.

(3) the mining cost of its ore.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D5 Which of the following statements concerning aluminium is / are correct?

(1) Aluminium was used earlier than iron in the history of mankind.

(2) Aluminium is more abundant than iron in the Earth’s crust.

(3) Aluminium can be extracted by electrolysis of its oxide.

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

D

9.6: How long will metal resources last?

9.7: Conservation of metal resources

(CDC guide: Limited reserve of metals and their conservations)

1 Which of the following statements is correct?

A Aluminium is the only metal that is recycled to a large extent.

B The resources of iron will last for about 1000 years.

C Recycling helps reduce the waste disposal problems.

D It is economical to recycle metals because the cost of extraction is higher than the cost of

recycling.

C2 Which of the following materials is frequently used to replace metals for making water pipes?

A Glass

B Plastic

C Wood

D Paper

B3 Which of the following statements concerning the recycling of metals is INCORRECT?

A Recycling of used metals consumes less energy than extracting metals from their ores.

B It is difficult to sort out metals from household waste for recycling.

C All products made by recycled metals have bad quality.

D Recycling is important because resources of metals are limited.

C4 Which of the following are possible ways to conserve metals?

(1) Recycle used metals

(2) Reduce the use of metals

(3) Reuse metal articles

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D5 Which of the following methods will help to conserve aluminium?

(1) Recycle used aluminium foils

(2) Replace aluminium cans with glass bottles

(3) Reuse aluminium articles

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D6 Which of the following statements concerning the recycling of metals are correct?

(1) It is a method of conserving metal resources.

(2) It helps to reduce pollution.

(3) It can raise public awareness of conservation.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D

Unit 10

10.1: Comparing the reactivity of metals

10.2: How do metals react with oxygen?

10.3: How do metals react with water or steam?

10.4: How do metals react with dilute acids?

(CDC guide: Reactions of metals with oxygen, water and dilute acid)

1 Which of the following metals burns with a brick-red flame?

A Potassium

B Sodium

C Calcium

D Magnesium

C2 The oxide of a metal is orange when it is hot but yellow when it is cold. The metal is

A potassium.

B zinc.

C calcium.

D lead.

D3 Which of the following metals does NOT give any observable changes upon heating?

A Platinum

B Iron

C Mercury

D Calcium

A4 Sodium should be stored

A in a brown bottle.

B in an air-tight flask.

C in paraffin oil

D in water.

C5 Which of the following metals can burn spontaneously in water to give a purple flame?

A Potassium

B Sodium

C Calcium

D Magnesium

A

6 Hydrogen can be prepared by using the following set-up:

Which metal is most suitable for this purpose?

A Potassium

B Calcium

C Magnesium

D Lead

B7 Consider the following experiment:

During the experiment, a gas is liberated. The gas can burn at the end of the delivery tube. X is

probably

A zinc.

B silver.

C lead.

D copper.

A8 Which of the following metals is most suitable for making a container to hold hot water?

A Aluminium

B Copper

C Magnesium

D Silver

B

9 Which of the following word equations is correct?

A Sodium + water sodium oxide + hydrogen

B Iron + water iron(II) hydroxide + hydrogen

C Magnesium + steam magnesium oxide + hydrogen

D Lead + steam lead(II) hydroxide + hydrogen

C10 Hydrogen can be prepared in the laboratory by reacting dilute sulphuric acid with

A sodium.

B zinc.

C lead.

D copper.

B11 Which of the following pairs of chemicals do NOT give hydrogen when reacted?

A Magnesium and dilute sulphuric acid

B Calcium and water

C Iron and steam

D Silver and dilute hydrochloric acid

D12 Metal X does NOT react with cold water but reacts readily with steam. Metal X is

probably

A calcium.

B copper.

C lead.

D magnesium.

D13 Results of some experiments on a metal X are shown below:

X burns when heated in air.

X reacts with water to give a hydroxide.

X cannot be extracted from its oxide by carbon reduction.

X could be

A aluminium.

B iron.

C magnesium.

D potassium.

D14 In an experiment, dilute hydrochloric acid was added to a test tube containing several small

pieces of zinc.

Which of the following observations could have been made during this experiment?

A There was no observable change.

B A thick white precipitate formed.

C A colourless gas was produced and the test tube cooled off.

D A colourless gas was produced and the test tube warmed up.

D15 Which of the following pairs of substances would NOT react together?

A Calcium and dilute hydrochloric acid

B Calcium carbonate and dilute nitric acid

C Copper and dilute sulphuric acid

D Copper(II) carbonate and dilute hydrochloric acid

C16 Barium (Ba) is a Group II element of the periodic table. Its relative atomic mass is greater than

that of calcium. Which of the following statements concerning barium is INCORRECT?

A Barium reacts vigorously with water.

B Barium reacts with water to give barium oxide.

C Barium sinks in water.

D The melting point of barium is lower than that of calcium.

B17 X is an element. It forms a cation X2+ with an electronic arrangement of 2, 8, 8. Which of the

following statements concerning X is correct?

A X gives a purple flame when burned in air.

B X sinks in water.

C X can be extracted from its ore by carbon reduction.

D The reaction between X and dilute sulphuric acid can be used to prepare hydrogen.

B18 In which of the following cases will a reaction take place?

(1) Adding zinc into cold water

(2) Adding iron into dilute sulphuric acid

(3) Heating copper(II) oxide with carbon

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

D19 Which of the following metals would form an oxide with different colours at different

temperatures?

(1) Iron

(2) Lead

(3) Zinc

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

C20 Which of the following metals do(es) NOT burn on heating?

(1) Calcium

(2) Lead

(3) Mercury

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

D21 Which of the following metals are shiny when freshly cut but rapidly tarnishes in air?

(1) Potassium

(2) Sodium

(3) Zinc

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

A22 Which of the following statements concerning sodium are correct?

(1) Sodium can be cut by a knife.

(2) Sodium tarnishes rapidly in air.

(3) Sodium burns with a golden yellow flame.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D23 Which of the following metals can react with cold water readily to give hydrogen?

(1) Calcium

(2) Magnesium

(3) Zinc

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

A24 Which of the following metals do(es) NOT react with water but react(s) with steam?

(1) Iron

(2) Lead

(3) Mercury

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

A25 A piece of magnesium ribbon is placed in a test tube containing dilute hydrochloric acid.

Which of the following statements are correct?

(1) Magnesium dissolves to give a colourless solution.

(2) A ‘pop’ sound results when a glowing splint is placed near to the mouth of the test tube.

(3) The resulting solution is magnesium chloride solution.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

B26 Which of the following actions is dangerous and should NOT be attempted in the school

laboratory?

(1) Adding sodium to dilute sulphuric acid

(2) Disposing a piece of potassium to a rubbish bin

(3) Heating calcium in steam

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

A27 Which of the following pairs of substances can react with each other?

(1) Aluminium and steam

(2) Magnesium and dilute sulphuric acid

(3) Lead and hot water

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

A28 Cold and dilute sulphuric acid has NO observable reaction with

(1) calcium.

(2) lead.

(3) copper.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D29 When a small piece of sodium is put into a trough of water, a reaction occurs. Which of the

following statements concerning this reaction is / are correct?

(1) An explosion occurs.

(2) Heat is given out.

(3) An alkaline solution is formed.

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

D30 In which of the following experiments would hydrogen be produced?

(1) Electrolysis of sea water

(2) Passing steam over magnesium

(3) Adding iron to dilute hydrochloric acid

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D31 A counterfeit gold coin is made from an alloy of copper and zinc. Which of the following

methods can be used to distinguish the counterfeit coin from a gold coin?

(1) Comparing their densities

(2) Treating both coins with dilute hydrochloric acid

(3) Comparing their electrical conductivity

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D

10.5: The reactivity series

10.8: What determines the reactivity of a metal?

(CDC guide: Metal reactivity series and the tendency of metal to form positive

ion)

1 Which of the following shows the correct descending order of reactivity of metals?

A Fe, Zn, Ag, Cu

B Al, Fe, Cu, Au

C K, Na, Al, Ca

D Mg, Al, Pb, Zn

B2 Potassium is more reactive than calcium because

A potassium loses electrons more readily than calcium does.

B potassium has a lower melting point than calcium.

C potassium has a lower density than calcium.

D calcium ions are more stable than potassium ions.

A

3 Which of the following combinations is correct?

The ease of losing electrons of metals The reactivity of metals

A Increases across a period Decreases down a group

B Decreases across a period Increases down a group

C Increases across a period Increases down a group

D Decreases across a period Decreases down a group

B4 Which of the following statements are correct?

(1) Metals react by losing electrons.

(2) Metals react by forming cations.

(3) The more reactive the metal is, the more readily it loses electrons.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D5 Which of the following properties are related to the metal reactivity series?

(1) The ease of extraction of a metal

(2) The method of storing a metal

(3) The stability of the compounds of a metal

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D6 Rubidium is a Group I element below potassium in the periodic table. Which of the following

statements concerning rubidium are correct?

(1) Rubidium loses electrons more readily than potassium does.

(2) Rubidium reacts with water to give rubidium hydroxide and hydrogen.

(3) Rubidium can be extracted from its oxide by reduction with carbon.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

A

10.6: What is a chemical equation?

10.7: How to write balanced chemical equations?

10:10: Ionic equations

(CDC guide: Chemical equations and ionic equations)

1 Which of the following combinations of state symbols is correct for this reaction?

2Na + 2H2O 2NaOH + H2

A (s), (l), (aq), (g)

B (s), (aq), (s), (g)

C (l), (aq), (s), (l)

D (l), (l), (aq), (l)

A2 In limestone areas, calcium carbonate in the rock reacts with rainwater containing dissolved

carbon dioxide as shown by the following equation:

CaCO3(x) + CO2(g) + H2O(y) Ca(HCO3)2(z)

Which of the following combinations is correct?

x y z

A aq l s

B aq aq s

C s aq aq

D s l aq

D3 Solid sodium hydrogencarbonate decomposes upon heating according to the following

equation:

heat

2NaHCO3(s) Na2CO3(x) + CO2(y) + H2O(z)


x y z

A aq g aq

B aq aq l

C s g l

D s aq aq

C4 Iron can be produced from iron(III) oxide by the following reaction:

heat

Fe2O3(x) + 3CO(y) 2Fe(s) + 3CO2(z)


x y z

A s aq aq

B s g g

C aq aq aq

D aq g g

B5 Consider the following reaction:

CaCO3(x) + 2HCl(y) CaCl2(aq) + CO2(g) + H2O(z)


x y z

A aq l aq

B aq aq l

C s aq l

D s l aq

C6 Consider the following chemical equation:

2HNO3(aq) + Na2CO3(x) 2NaNO3(y) + H2O(z) + CO2(g)


x y z

A aq s l

B aq aq aq

C s aq l

D s s aq


heat

4Fe(OH)2(x) + O2(g) 2Fe2O3(y) + 4H2O(z)


x y z

A s s l

B s aq aq

C aq s aq

D aq aq l

A8 The reaction between magnesium hydrogencarbonate solution and zinc sulphate solution can

be represented by the following equation:

Mg(HCO3)2(aq) + ZnSO4(aq) MgSO4(x) + ZnCO3(y) + H2O(z) + CO2(g)


x y z

A aq s aq

B s aq aq

C aq s l

D s aq l


Na2S2O3(aq) + 2HCl(aq) 2NaCl(x) + SO2(aq) + H2O(y) + S(z)


x y z

A l aq s

B l aq aq

C aq l aq

D aq l s

D10 When sodium hypochlorite solution is exposed to sunlight, it decomposes according to the

following equation:

xNaOCl(aq) yNaCl(aq) + zO2(g)


x y z

A 2 1 1

B 2 2 1

C 1 2 1

D 2 1 2

B11 The reaction between hydrogen iodide and concentrated sulphuric acid can be represented by

the following equation:

xHI(aq) + H2SO4(l) H2S(g) + yH2O(l) + zI2(aq)

What is the value of x?

A 4

B 6

C 8

D 10

C12 One way to dissolve gold (Au) is to react it with Aqua-regia, a mixture of concentrated nitric

acid and concentrated hydrochloric acid. The equation for the reaction is:

Au(s) + xHNO3(aq) + yHCl(aq) HAuCl4(aq) + zH2O(l) + zNO2(g)

What is the value of z?

A 2

B 3

C 4

D 5

B13 The following equation represents the reaction between an oxide of lead and hydrogen:

heat

Pb3O4(s) + xH2(g) yPb(s) + zH2O(l)


x y z

A 2 3 2

B 4 2 3

C 4 3 4

D 2 4 3

C14 Magnesium nitride is decomposed by water according to the following equation:

Mg3N2(s) + xH2O(l) yMg(OH)2(s) + zNH3(g)


x y z

A 6 3 2

B 6 2 3

C 3 6 2

D 3 2 6

A15 Consider the following chemical equation:

xH2S(g) + 2KMnO4(aq) + yH2SO4(aq) xS(s) + zH2O(l) + 2MnSO4(aq) + K2SO4(aq)


x y z

A 8 5 3

B 8 3 5

C 5 3 8

D 5 8 3


2HNO3(aq) + xFeSO4(aq) + yH2SO4(aq) zFe2(SO4)3(aq) + 4H2O(l) + 2NO(g)


x y z

A 2 1 1

B 4 3 2

C 6 2 3

D 6 3 3

D17 The action of dilute nitric acid on copper can be represented by the following equation:

xCu(s) + yHNO3(aq) xCu(NO3)2(aq) + 4H2O(l) + zNO(g)

The values of x, y and z in the balanced equation should be

A 3, 4 and 1.

B 3, 8 and 2.

C 4, 3 and 2.

D 8, 3 and 2.

B18 The action of dilute sulphuric acid on iron(III) hydroxide can be represented by the following

equation:

wFe(OH)3(s) + xH2SO4(aq) yFe2(SO4)3(aq) + zH2O(l)

The values of w, x, y and z in the balanced equation should be

A 1, 3, 1 and 2.

B 2, 3, 2 and 6.

C 2, 3, 1 and 6.

D 2, 6, 1 and 3.

C19 Consider the following ionic equation:

Cu(s) + 4H+(x) + 2NO3-(aq) Cu2+(y) + 2NO2(z) + 2H2O(l)


x y z

A l aq aq

B l l g

C aq aq l

D aq aq g

D20 The reaction between zinc nitrate solution and sodium hydrogencarbonate solution can be

represented by the ionic equation below:

Zn2+(aq) + 2HCO3-(aq) ZnCO3(x) + H2O(y) + CO2(z)


x y z

A aq l g

B aq aq aq

C s aq g

D s l g

D21 Consider the following ionic equation:

2MnO4-(aq) + xH+(aq) + 2yI- (aq) 2Mn2+(aq) + yI2(aq) + zH2O(l)


x y z

A 4 1 2

B 4 3 2

C 8 3 4

D 16 5 8

D22 Which of the following equations CANNOT be rewritten into an ionic equation?

(1) Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)

heat

(2) 2Pb(NO3)2(s) 2PbO(s) + 4NO2(g) + O2(g)

(3) Ca(OH)2(aq) + CO2(g) CaCO3(s) + H2O(l)

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

D23 The following equation is related to the manufacture of ammonia:

N2(g) + 3H2(g) 2NH3(g)

Which of the following statements can be deduced from the above equation?

(1) The reaction is reversible.

(2) The forward reaction and backward reaction occur simultaneously.

(3) A catalyst should be used.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

A

10.9: Displacement reactions

(CDC guide: Displacement reactions and their interpretations based on

reactivity series)

1 Which of the following ions can be displaced by lead?

A Fe2+(aq)

B Cu2+(aq)

C Mg2+(aq)

D Al3+(aq)

B2 In which of the following cases will a reaction take place?

A Cu(s) + Zn2+(aq)

B Ag(s) + Fe2+(aq)

C Al(s) + Cu2+(aq)

D Pb(s) + Mg2+(aq)

C3 Which of the following metals will displace aluminium from aluminium sulphate solution?

A Zinc

B Iron

C Magnesium

D Lead

C4 Silver nitrate solution can be stored in metal containers made of

A aluminium.

B zinc.

C copper.

D gold.

D5 When a piece of lead is dropped into an aqueous solution of compound X, the lead gradually

dissolves. X could be

A copper(II) nitrate.

B zinc nitrate.

C magnesium sulphate.

D ammonium chloride.

A6 Tin is in between iron and lead in the reactivity series. Which of the following can be deduced

from this information?

A Tin reacts with steam vigorously to give an oxide.

B Tin displaces iron from iron(II) nitrate solution.

C Tin reacts with oxygen more readily than lead does.

D A tin ion carries 2 positive charges.

C7 A copper wire is put into silver nitrate solution in a test tube. What will be observed after a

few minutes?

Colour change of solution Copper

A Blue to pale blue Brown solids formed on copper surface

B Blue to pale blue Grey solids formed on copper surface

C Remains unchanged Shiny solids formed on top of the solution

D Colourless to blue Grey solids formed on copper surface

D

8 Which of the following will NOT react with each other?

A Zinc and steam

B Iron and dilute sulphuric acid

C Silver and copper(II) sulphate solution

D Lead and oxygen

C9 In each of the four solutions shown below, a strip of magnesium is added.


Tube Observation

A I Grey coating on magnesium

B II Brown coating on magnesium

C III Bubbles are given off

D IV Grey coating on magnesium

A10 Which of the following statements concerning lead is correct?

A It can be obtained by heating lead(II) oxide strongly in air.

B It can displace zinc from zinc nitrate solution.

C It shows moderate reaction with steam.

D Its oxide is yellow when cool.

D11 Which of the following equations represents a displacement reaction that would NOT occur at

room temperature?

A Pb(s) + Zn2+(aq) Pb2+(aq) + Zn(s)

B Mg(s) + Fe2+(aq) Mg2+(aq) + Fe(s)

C Fe(s) + Cu2+(aq) Fe2+(aq) + Cu(s)

D Zn(s) + 2Ag+(aq) Zn2+(aq) + 2Ag(s)

A12 Zinc nitrate solution should NOT be stored in

(1) a magnesium container.

(2) a plastic container.

(3) a zinc container.

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

A13 Which of the following are correct when excess iron is added to lead(II) nitrate solution?

(1) A pale green solution is obtained.

(2) Some grey solids are deposited on the iron surface.

(3) A gas is evolved.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

A14 X is an element with an electronic arrangement of 2, 8, 1. Which of the following statements

concerning X is / are correct?

(1) X burns in air with a golden yellow flame.

(2) X is extracted by reduction with carbon.

(3) A gas is given off when X reacts with zinc sulphate solution.

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

C15 A piece of magnesium is dropped into a beaker of copper(II) sulphate solution. Which of the

following will be observed?

(1) Gas bubbles are evolved.

(2) A brown layer forms on the surface of magnesium.

(3) The colour of the blue solution fades.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

C

10.11: Relationship between the extraction method and position of metals in the

reactivity series

(CDC guide: Relation between the extraction method for a metal and its position

in the metal reactivity series)

1 Which of the following metal oxides is most difficult to be reduced?

A MgO

B CuO

C ZnO

D FeO

A2 How could calcium be extracted from solid calcium chloride?

A By displacement reaction with magnesium

B By melting it and passing electricity through the molten calcium chloride

C By passing electricity through solid calcium chloride

D By strongly heating calcium chloride with carbon

B3 Tin is just below iron in the metal reactivity series. Oxide of tin can be reduced to tin by

A heating the oxide with lead.

B heating the oxide strongly.

C heating the oxide with carbon.

D electrolysis of the aqueous solution of the oxide.

C4 Metal X is just below zinc in the reactivity series. Which of the following reactions are most

likely to occur?

heat

(1) 2XO(s) + C(s) 2X(s) + CO2(g)

heat

(2) 2XO(s) 2X(s) + O2(g)

(3) X(s) + Cu2+(aq) X2+(aq) + Cu(s)

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

B5 A metal at the top of the reactivity series would be expected to

(1) have a shiny appearance.

(2) form an oxide which is stable to heat.

(3) be extracted by heating its ore with carbon.

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

B6 Nickel is in between iron and lead in the reactivity series. Which of the following

statements concerning nickel are probably correct?

(1) Nickel(II) oxide can be reduced by carbon.

(2) Nickel can displace silver from silver nitrate solution.

(3) Nickel reacts with dilute sulphuric acid to give hydrogen.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D7 Metal X reacts with hot water more readily than metal Y does. Which of the following

statements are probably correct?

(1) X displaces Y from the solution of nitrate of Y.

(2) It is more difficult to reduce the oxide of X when compared to the oxide of Y.

(3) Both X and Y react with steam to form hydroxides.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

A

10.12: Prediction of metal reactions using the reactivity series

(CDC guide: Prediction of metal reactions using the reactivity series)

1 Chromium lies between zinc and iron in the reactivity series. Which of the following

statements is INCORRECT?

A When chromium powder is added to copper(II) sulphate solution, a brown deposit will

form.

B Chromium reacts with dilute hydrochloric acid to liberate hydrogen.

C Magnesium is more reactive than chromium.

D Chromium is usually obtained by electrolysis of its molten ore.

D2 Metal X is more reactive than platinum but less reactive than iron. Which of the following

statements is most likely to be correct?

A X burns vigorously in air to form an oxide.

B X reacts with dilute hydrochloric acid vigorously.

C X displaces iron from iron(II) sulphate solution.

D The oxide of X can be reduced by heating with carbon.

D3 X, Y and Z are metals. X displaces Y from the solution of chloride of Y, but has no reaction

with the solution of nitrate of Z. The reactivity of the three metals in descending order is

A X, Y, Z.

B X, Z, Y.

C Z, X, Y.

D Z, Y, X.

C4 X, Y and Z are metals. The oxides of X and Y can be reduced by heating with carbon, but the

oxide of Z cannot. Y displaces X from a solution of nitrate of X. The descending order of

reactivity of the three metals is

A X, Y, Z.

B X, Z, Y

C Z, X, Y.

D Z, Y, X.

D5 X, Y and Z are metals. Metals Y and Z have no reaction with steam while metal X reacts with

water to liberate hydrogen. Only metal Y is found free in nature. The order of increasing

reactivity of the three metals is

A X, Y, Z.

B X, Z, Y.

C Y, X, Z.

D Y, Z, X.

D6 Metals X and Y both have no reaction with cold water. X reduces iron(II) oxide on heating.

Copper displaces Y from a solution of nitrate of Y. The descending order of reactivity of the

four metals is

A X, Fe, Cu, Y.

B Fe, X, Cu, Y.

C X, Fe, Y, Cu.

D Y, Cu, Fe, X.

A7 Metal X reacts with dilute hydrochloric acid to liberate hydrogen, but metals Y and Z have no

reaction with the acid. The oxide of Y decomposes on heating but the oxide of Z does not. The

order of decreasing reactivity of the three metals should be

A X, Y, Z.

B X, Z, Y.

C Z, Y, X.

D Z, X, Y.

B8 The properties of four metals are listed in the table below:

Metal Properties

W does not react with dilute hydrochloric acid

X burns in air to give an orange solid, which becomes yellow on cooling

Y reacts with steam slowly but not with cold water

Z can be extracted from its ore by electrolysis only

The order of decreasing reactivity is probably

A X, Y, W, Z.

B X, Z, Y, W.

C Z, Y, X, W.

D Z, X, Y, W.

CDirections: Questions 9 and 10 refer to the results of an experiment for three metals X, Y and

Z.

Action of metal on copper (II) sulphate solution

X Copper is deposited.

Y A gas is evolved.

Z No reaction

9 The order of increasing reactivity of the three metals should be

A Y < X < Z.

B X < Z < Y.

C Z < Y < X.

D Z < X < Y.

D10 Y could be

A zinc.

B magnesium.

C sodium.

D copper.

C11 X, Y and Z are metals. Metal Y reacts with dilute hydrochloric acid to liberate hydrogen while

metals X and Z do not. Only metal X is known to be used since ancient times. The descending

order of reactivity of the three metals is

A Y, X, Z.

B Y, Z, X.

C Z, X, Y.

D Z, Y, X.

B12 A student performed tests to investigate the reactivity of three metals. In each test, a metal

strip was placed in a solution containing ions of a different metal. The results are shown in the

diagrams.

What is the order of reactivity of the metals, based on these results?

A X > Z > Y

B Y > X > Z

C Z > Y > X

D Z > X > Y

DDirections: Questions 13 and 14 refer to the results of experiments for three

metals X, Y and Z, and their compounds.

Metal Reaction with

cold water

Action of heat

on metal oxide

X No reaction No reaction

Y Hydrogen liberated No reaction

Z No reaction Metal and oxygen formed

13 The descending order of reactivity of the three metals is

A X, Y, Z.

B X, Z, Y.

C Y, X, Z.

D Y, Z, X.

C14 Which of the following statements concerning Y are probably correct?

(1) Y reacts with water to give a hydroxide.

(2) Y is extracted by electrolysis of its molten ore.

(3) Y has been used by humans since ancient times.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

A15 In which of the following experiments would a metal be produced?

(1) Heating iron(III) oxide with aluminium

(2) Adding zinc to silver nitrate solution

(3) Heating copper with magnesium oxide

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

A16 Caesium is an alkali metal. Which of the following statements are correct?

(1) It loses electrons more readily than potassium does.

(2) It reacts with oxygen vigorously.

(3) It reacts with water to give an alkaline solution.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D17 Barium is a Group II element. Which of the following statements concerning barium are

correct?

(1) It reacts with dilute hydrochloric acid to give hydrogen.

(2) It is extracted by electrolysis of its molten ore.

(3) It reacts with water to give barium oxide.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

A18 Strontium is a Group II element. Which of the following statements concerning strontium

are correct?

(1) It can be obtained by heating strontium oxide with carbon.

(2) It reacts with water readily.

(3) It is more reactive than calcium.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

C19 Tin is a metal just above lead in the reactivity series. Which of the following statements

concerning tin are probably correct?

(1) It is extracted by electrolysis of its molten ore.

(2) An oxide is formed when tin is heated in air.

(3) It shows no reaction with cold water.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

C20 X and Y are two different metals. Which of the following show(s) that Y is more reactive

than X?

(1) X forms an ion with a charge of +2 while Y forms an ion with a charge of +3.

(2) The oxide of X undergoes decomposition upon strong heating but the oxide of Y does

not.

(3) X reacts with steam but Y does not.

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

B

Unit 11

11.1: Calculating the quantity of substances

11.2: Counting numbers by weighing

11.3: What is a mole?

11.4: What is molar mass?

(CDC guide: Quantitative relationship of the reactants and products in a

reaction as revealed from a chemical equation & Mole, Avogadro's constant and

molar mass)

1 1 mole of potassium oxide contains

A 1 mole of molecules.

B 2 moles of cations.

C 2 moles of anions.

D 3 moles of atoms.

B2 How many atoms are present in 0.600 mole of carbon dioxide molecules?

(Avogadro constant = 6.02 1023 mol-1)

A 0.6

B 1.8

C 3.61 1023

D 10.8 1023

D3 3 moles of magnesium chloride contains

A 3 moles of molecules.

B 6 moles of cations.

C 6 moles of anions.

D 9 moles of atoms.

C4 Consider the chemical equation:

2Ca(s) + O2(g) 2CaO(s)

Which of the following statements are correct?

(1) Calcium and oxygen are reactants.

(2) Calcium oxide is the product.

(3) 2 moles of calcium react with 1 mole of oxygen to give 2 moles of calcium oxide.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D5 Which of the following statements are correct?

(1) One mole is the quantity of a substance that contains Avogadro number of particles.

(2) One mole of zinc and one mole of iron have different masses.

(3) The molar mass of a substance is the mass in gram of one mole of it.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D6 The Avogadro constant

(1) has the numerical value of 6.02 1023.

(2) varies with temperature and pressure.

(3) is represented by the symbol L.

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

C7 The molecular formula of ozone is O3. Which of the following statements concerning 1 mole

of ozone is / are correct?

(Avogadro constant = 6.02 1023 mol-1; relative atomic mass: O = 16.0)

(1) Its mass is 48.0 g.

(2) It contains 3 moles of molecules.

(3) It contains 3 6.02 1023 atoms.

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

C8 Which of the following statements concerning 1 mole of magnesium is / are correct?

(Avogadro constant = 6.02 1023 mol-1; relative atomic mass: Mg = 24.3)

(1) It can form 1 mole of Mg2+ ions.

(2) It can form 2 6.02 10 23Mg2+ ions.

(3) The mass of 1 mole of Mg2+ ions is 48.6 g.

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

A9 Which of the following statements concerning 1 mole of sulphur dioxide are correct?

(Avogadro constant = 6.02 1023 mol-1; relative atomic masses: O = 16.0, S = 32.1)

(1) It contains 3 moles of atoms.

(2) It contains 3 6.02 1023 ions.

(3) Its mass is 64.1 g.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

B

11.5: Calculations involving moles and masses

(CDC guide: Calculations related to moles and reacting masses)

1 If 2.00 g of oxygen gas contains x molecules, how many molecules are present in 28.0 g of

nitrogen gas?

(Relative atomic masses: N = 14.0, O = 16.0)

A x

B 4x

C 8x

D 16x

D2 If there are x molecules in 17.75 g of chlorine, how many molecules are present in 8.00 g of

sulphur dioxide ?

(Relative atomic masses: O = 16.0, S = 32.1, Cl = 35.5)

A x/4

B x/2

C x

D 2x

B3 The molecular formula of a gas is X3. If the Avogadro number is L mol-1, how many atoms are

there in 48.0 g of X3?

(Relative atomic mass: X = 16.0)

A 1/2 L

B L

C 2 L

D 3 L

D4 If 2.0 g of carbon monoxide gas contain x molecules, how many molecules are present in 1.0 g

of hydrogen gas?

(Relative atomic masses: H = 1.0, C = 12.0, O = 16.0)

A 3.5x

B 5.5x

C 7x

D 11x

C5 Which of the following gases, each having a mass of 3.00 g, has the largest number of

molecules at room temperature and pressure?

(Relative atomic masses: H = 1.0, C = 12.0, O = 16.0, F = 19.0, Ar = 40.0)

A Oxygen

B Hydrogen fluoride

C Carbon dioxide

D Argon

B6 Which of the following gases contains the largest number of molecules at room temperature

and pressure?

(Relative atomic masses: H = 1.0, C = 12.0, N = 14.0, O = 16.0, F = 19.0, Cl = 35.5)

A 4.0 g of hydrogen chloride

B 18.0 g of ammonia

C 38.0 g of fluorine

D 58.0 g of carbon dioxide

D7 The molecular formula of a gas is X2. If the relative atomic mass of X is 14.0, what is the

number of molecules in 112 g of the gas?


A 4

B 8

C 4 6.02 1023

D 8 6.02 1023

C8 The formula of ozone is O3. If 1 mole of ozone contains y atoms, how many atoms will 2

moles of oxygen gas contain?

A

B y

C

D 4y

C9 Element X forms two oxides, XO2 and XO3. If 1 mole of XO2 contains n atoms, 3 moles of

XO3 would contain

A 3n atoms.

B 4n atoms.

C 5n atoms.

D 6n atoms.

B10 Which of the following gases contains the same number of atoms as 2.20 g of carbon dioxide?

(Relative atomic masses: H = 1.0, C = 12.0, N = 14.0, O = 16.0, F = 19.0)

A 3.40 g of ammonia

B 2.30 g of nitrogen dioxide

C 0.30 g of hydrogen

D 1.90 g of fluorine

B11 Metal X forms an oxide. 32.0 g of this oxide contains 23.2 g of X. What is the mole ratio of X

to oxygen in the oxide?

(Relative atomic masses: O = 16.0, X = 56.0)

A 1 : 1

B 1 : 2

C 2 : 3

D 3 : 4

D

12 An oxide of element X has the formula X2O3. 14.3 g of this oxide contains 7.56 g of X. What

is the relative atomic mass of X?

(Relative atomic mass: O = 16.0)

A 12.0

B 18.0

C 27.0

D 36.0

C13 A solid mixture of iron(II) nitrate and iron(II) carbonate contains 1.0 mole of nitrate ions and

1.2 moles of iron(II) ions. What is the number of moles of carbonate ions in the mixture?

A 0.35

B 0.70

C 1.4

D 1.7

B14 What is the mass of oxygen in 24.0 g of pure nitric acid (HNO3)?

(Relative atomic masses: H = 1.0, N = 14.0, O = 16.0)

A 6.10 g

B 8.00 g

C 12.2 g

D 18.3 g

D15 What mass of water of crystallization is contained in 30.0 g of XSO45H2O with a molar mass

of 250.1 g mol-1?

(Relative atomic masses: H = 1.0, O = 16.0)

A 10.8 g

B 18.0 g

C 14.4 g

D 21.6 g

A

16 Plaster of Paris is used for setting broken limbs. Its formula is CaSO4 H2O. When water is

added, it sets to give gypsum, CaSO42H2O. What is the minimum mass of water needed to

set 0.500 kg of plaster of Paris?

(Relative atomic masses: H = 1.0, O = 16.0, S = 32.1, Ca = 40.1)

A 62.0 g

B 93.0 g

C 124 g

D 290 g

B17 The relative atomic masses of carbon and oxygen are 12.0 and 16.0 respectively. Which of the

following statements concerning 88.0 g of carbon dioxide is correct?


A It contains 4 moles of oxygen atoms.

B It contains 4 moles of molecules.

C It contains 6 6.02 1023 molecules.

D It contains 8 6.02 1023 atoms.

A18 Which of the following statements concerning 0.50 mole of nitrogen gas are correct?

(1) It contains the same number of atoms as 4.0 g of helium gas.

(2) It has a mass of 7.0 g.

(3) It contains 3.01 1023 molecules of nitrogen.

(Relative atomic masses: He = 4.0, N = 14.0; Avogadro constant = 6.02 1023 mol-1)

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

B19 1 mole of sulphur atoms has a mass twice that of 1 mole of oxygen atoms. Which of the

following statements is / are correct?

(1) 2 g of sulphur contains twice the number of atoms as 1 g of oxygen.

(2) The number of atoms contained in 1 mole of sulphur atoms is the same as that

contained in 1 mole of oxygen atoms.

(3) The number of S2- ions formed from 1 mole of sulphur atoms is twice that of O2-

ions formed from 1 mole of oxygen atoms.

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

B

11.6: Percentage by mass of an element in a compound

(CDC guide: Percentage by mass of an element in a compound )

1 What is the percentage by mass of water of crystallization in FeSO47H2O?

(Relative atomic masses: H = 1.0, O = 16.0, S = 32.1, Fe = 55.8)

A 45.3 %.

B 56.0 %.

C 72.0 %.

D 84.6 %.

A2 What is the percentage by mass of X in K2X2O7?

(Relative atomic masses: O = 16.0, K = 39.1, X = 52.0)

A 17.7 %

B 25.1 %

C 35.4 %

D 40.8 %

C3 Which of the following fertilizers contains the lowest percentage by mass of nitrogen?

(Relative atomic masses: H = 1.0, N = 14.0, O = 16.0, Na = 23.0, S = 32.1, Cl = 35.5,

K = 39.1)

A Potassium nitrate

B Sodium nitrate

C Ammonium chloride

D Ammonium sulphate

A4 Assuming that the effectiveness of a nitrogen-containing fertilizer is proportional to the

percentage by mass of nitrogen in the compound, which of the following compounds is the

most effective fertilizer?

Relative molecular mass

A CO(NH2)2 60.0

B NH4NO3 80.0

C NaNO3 85.0

D (NH4)2HPO4 132.0

A5 An ore sample contains 75.0% by mass of AlCl3 while the other ingredients do not contain

aluminium. What is the percentage by mass of aluminium in the sample?

(Relative atomic masses: Al = 27.0, Cl = 35.5)

A 15.2%.

B 25.2%.

C 35.2%.

D 45.2%.

A6 A silver coin, with a mass of 12.0 g, was dissolved completely in concentrated nitric acid to

give silver nitrate solution. When excess potassium chloride solution was added to the

resulting solution, 14.4 g of a white precipitate were obtained. What is the percentage by mass

of silver in the coin?

(Relative atomic masses: Cl = 35.5, Ag = 107.9)

A 45.0%

B 60.0%

C 75.0%

D 90.0%

D7 A salt, KClMgCl2nH2O, contains 38.9% by mass of water of crystallization. What is the

value of n?

(Relative atomic masses: H = 1.0, O = 16.0, Mg = 24.3, K = 39.1, Cl = 35.5)

A 5

B 6

C 7

D 18

B8 The compound X2S contains 70.8% by mass of X. What is the relative atomic mass of X?

(Relative atomic mass: S = 32.1)

A 17.5

B 23.0

C 39.0

D 80.0

C9 XCl4 contains 16.5 % by mass of X. What is the relative atomic mass of X?

(Relative atomic mass: Cl = 35.5)

A 26.5

B 28.0

C 30.5

D 36.0

B10 An element forms an oxide X2O5, which contains 35.0% by mass of oxygen. What is the

relative atomic mass of X?


A 3.45

B 21.5

C 43.1

D 74.3

D11 A sample of paint pigment of mass 1.50 g is dissolved and the lead ions in it are separated by

precipitation as solid PbSO4. The precipitate has a mass of 0.0849 g. What is the percentage

by mass of lead in the pigment?

(Relative atomic masses: O = 16.0, S = 32.1, Pb = 207.2)

A 3.87%

B 5.66%

C 5.80%

D 12.7%

A

11.7: Determining the empirical formula of a compound from experimental data

(CDC guide: Empirical formulae derived from experimental data)

1 2 moles of atoms of X combines with 16.0 g of oxygen to form an oxide. What is the

empirical formula of this oxide?


A XO

B XO2

C XO3

D X2O

D2 A compound is formed when 71.0 g of chlorine combine with 48.0 g of oxygen. What is the

empirical formula of the compound?

(Relative atomic masses: O = 16.0, Cl = 35.5)

A ClO

B ClO2

C Cl2O

D Cl2O3

D3 Heating 4.80 g of an element X gives 9.60 g of its oxide. What is the empirical formula of the

oxide?

(Relative atomic masses: O = 16.0, X = 32.1)

A XO

B X2O

C XO2

D XO3

C4 A compound contains carbon and hydrogen only. If the percentage by mass of hydrogen in the

compound is 25.0%, what is its empirical formula?

(Relative atomic masses: H = 1.0, C = 12.0)

A CH

B CH2

C CH3

D CH4

D5 A compound contains 34.4% of nickel, 28.1% of carbon and 37.5% of oxygen by mass. What

is its empirical formula?

(Relative atomic masses: C = 12.0, O = 16.0, Ni = 58.7)

A NiCO

B Ni(CO)4

C NiCO3

D Ni(CO)2

B6 What is the empirical formula of a compound with the following composition by mass?

Na = 36.5% S = 25.4% O = 38.1%

(Relative atomic masses: O = 16.0, Na = 23.0, S = 32.1)

A NaSO3

B NaSO4

C Na2SO3

D Na2SO4

C7 Vitamin C contains 40.9% of carbon, 4.60% of hydrogen and 54.5% of oxygen by mass.

What is the empirical formula of vitamin C?

(Relative atomic masses: H= 1.0, C = 12.0, O = 16.0)

A CH2O

B C2H3O2

C C3H4O3

D C4H5O4

C8 32.2 g of an oxide of metal M, when completely reduced by carbon, produced 4.95 g of carbon

dioxide. What is the empirical formula of the oxide?

(Relative atomic masses: C = 12.0, O = 16.0, M = 63.5)

A MO

B M2O

C MO2

D M2O3

B9 A compound contains 18.2% of lithium, 71.2% of aluminium and 10.6% of hydrogen by mass.

What is its empirical formula?

(Relative atomic masses: H = 1.0, Li = 6.9, Al = 27.0)

A LiAlH2

B LiAlH4

C Li2AlH5

D Li3AlH5

B10 The relative atomic mass of metal X is 52.0. 33.8 g of X are allowed to react with steam.

The mass of oxide obtained is 49.4 g. What is the empirical formula of the oxide?


A X2O

B XO

C X2O3

D X3O4

C11 Metal X forms an oxide with the empirical formula X2O. Upon strong heating, the oxide

decomposes according to the following equation:

2X2O(s) 4X(s) + O2(g)

Complete decomposition of 55.7 g of the oxide gives 3.84 g of oxygen. What is the

relative

atomic mass of X?


A 54.0

B 108.0

C 162.0

D 216.0

B12 A compound contains carbon and hydrogen only. It contains 16.3% by mass of hydrogen.

The relative molecular mass of the compound is 86.0. What is its molecular formula?

(Relative atomic masses: H= 1.0, C = 12.0)

A C3H7

B C6H14

C C7H2

D C7H16

B13 A compound contains 54.5% by mass of carbon, 9.10% by mass of hydrogen and the rest

being oxygen. The relative molecular mass of this compound is 88.0. What is its molecular

formula?

(Relative atomic masses: H= 1.0, C = 12.0, O = 16.0)

A C2H4O

B C3H4O3

C C4H8O2

D C5H12O

C

11.8: Mole ratio in a balanced chemical equation

11.9: Chemical equations and reacting masses

11.10: Limiting reactants

11.11: Theoretical yield and actual yield

(CDC guide: Reacting masses from chemical equations)

1 24.4 g of a hydrated metal sulphate were heated to a constant mass. After cooling to room

temperature, the anhydrous metal sulphate weighed 11.9 g. How many moles of water of

crystallization are there in one mole of the hydrated metal sulphate?

(Relative formula / molecular masses: anhydrous metal sulphate = 120.4, water = 18.0)

A 4

B 5

C 7

D 10

C2 4.68 g of metal X combine with 2.16 g of oxygen to form an oxide in which the charge of the

ion of X is +3. What is the relative atomic mass of X?


A 11.6

B 34.7

C 52.0

D 104

C3 The formula of hydrated sodium carbonate crystals is Na2CO3xH2O. When 66.9 g of the

hydrated crystals are heated, 24.8 g of anhydrous sodium carbonate are produced. What is the

value of x?

(Relative atomic masses: H = 1.0, C = 12.0, O =16.0, Na = 23.0)

A 3

B 5

C 7

D 10

D4 What mass of iron is obtained when 0.400 mole of iron(III) oxide is completely reduced by

carbon monoxide?

(Relative atomic mass: Fe = 55.8)

A 33.6 g

B 44.6 g

C 67.2 g

D 96.1 g

B5 The formula of hydrated zinc sulphate is ZnSO4xH2O. On strong heating, 18.7 g of the

hydrated sulphate produces 8.19 g of water. What is the value of x?

(Relative atomic masses: H = 1.0, O = 16.0, S = 32.1, Zn = 65.4)

A 5

B 6

C 7

D 8

C6 The following equation represents the reaction of an oxide of iron with carbon:

Fe3O4(s) + 2C(s) 3Fe(s) + 2CO2(g)

What mass of iron would be obtained if 81.0 g of the oxide were consumed in the reaction?

(Relative atomic masses: O = 16.0, Fe = 55.8)

A 19.5 g

B 39.0 g

C 58.6 g

D 78.1 g

C

7 Aluminium can be produced from aluminium oxide by the following reaction:

Al2O3(s) + 3Mg(s) 2Al(s) + 3MgO(s)

What mass of aluminium oxide is required to produce 11.9 g of aluminium?

(Relative atomic masses: O = 16.0, Al = 27.0)

A 22.4 g

B 33.6 g

C 44.8 g

D 67.3 g

A8 NaHCO3 decomposes upon heating to form Na2CO3, CO2 and H2O. What is the mass of

Na2CO3 obtained if 126 g of NaHCO3 undergo complete decomposition?

(Relative atomic masses: H = 1.0, C = 12.0, O = 16.0, Na = 23.0)

A 79.5 g

B 84.0 g

C 106 g

D 159 g

A9 A solid mixture consists of 1.0 mole of calcium carbonate and 1.0 mole of sodium carbonate.

What is the least number of moles of hydrochloric acid required to liberate all the carbon

dioxide from the mixture?

A 1.5

B 2.0

C 3.0

D 4.0

D10 Consider the following equation:

2NH3(g) + 3CuO(s) N2(g) + 3H2O(l) + 3Cu(s)

What mass of ammonia would be required to give 0.450 mole of water in the reaction?

(Relative atomic masses: H = 1.0, N = 14.0)

A 5.10 g

B 7.65 g

C 11.4 g

D 15.3 g

A11 Ammonium dichromate ((NH4)2Cr2O7) decomposes on heating to give chromium(III) oxide,

water and nitrogen. What mass of water is obtained when 277 g of (NH4)2 Cr2O7 undergo

complete decomposition?

(Relative atomic masses: H = 1.0, N = 14.0, O = 16.0, Cr = 52.0)

A 19.8 g

B 39.6 g

C 79.2 g

D 158 g

C12 Consider the following equation:

X2(g) + 3Y2(g) 2XY3(g)

If 4 moles of X2(g) react with 6 moles of Y2(g), what is the number of moles of XY3(g)

formed?

A 2

B 4

C 8

D 10

B13 The following equation represents the reaction of propane (C3H8) with oxygen:

C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(l)

What is the mass of carbon dioxide formed when 3 moles of propane react with 10 moles of

oxygen?

(Relative atomic masses: C = 12.0, O = 16.0)

A 132 g

B 264 g

C 308 g

D 396 g

B

14 4.00 moles of hydrochloric acid react with 72.0 g of magnesium. What is the mass of

hydrogen produced?

(Relative atomic masses: H = 1.0, Mg = 24.3)

A 2.00 g.

B 3.00 g.

C 4.00 g.

D 6.00 g.

C15 Hydrazine (N2H4) is used as rocket fuel. It reacts with oxygen according to the following

equation:

N2H4(l) + O2(g) N2(g) + 2H2O(l)

In a particular rocket engine, 2.40 g of hydrazine and 3.40 g of oxygen are allowed to

react.

What is the mass of water produced?

(Relative atomic masses: H = 1.0, N = 14.0, O = 16.0)

A 1.35 g

B 1.90 g

C 2.70 g

D 3.80 g

C16 Sodium and chlorine react according to the following equation:

2Na(s) + Cl2(g) 2NaCl(s)

12.5 g of sodium and 25.5 g of chlorine are allowed to react. What is the mass of sodium

chloride formed?

(Relative atomic masses: Na = 23.0, Cl = 35.5)

A 31.8 g

B 42.0 g

C 63.5 g

D 84.0 g

A17 In the combustion of a certain fuel, 16.0 g of carbon dioxide are produced. This represents a

75.0% yield. What is the theoretical yield of carbon dioxide?

A 12.0 g

B 21.3 g

C 32.0 g

D 44.3 g

B18 Calcium carbonate can be decomposed by heating. When 24.8 g of calcium carbonate were

heated, 13.1 g of calcium oxide were obtained. What is the percentage yield of calcium oxide?

(Relative atomic masses: C = 12.0, O = 16.0, Ca = 40.1)

A 24.8%

B 52.8%

C 72.4%

D 94.4%

D19 Manufacturing ammonia in industry involves the reaction between nitrogen and hydrogen.

N2(g) + 3H2(g) 2NH3(g)

A sufficient amount of hydrogen is allowed to react with 10.0 moles of nitrogen. Suppose that

the conversion of nitrogen to ammonia is 15.0%. What is the mass of ammonia formed?

(Relative atomic masses: H = 1.0, N = 14.0)

A 20.0 g

B 51.0 g

C 113 g

D 340 g

B20 When copper is heated with an excess of sulphur, copper(I) sulphide is formed according

to the following equation:

2Cu(s) + S(s) Cu2S(s)

In a particular experiment, 2.40 g of copper were heated with excess sulphur to obtain

2.85 g

of copper(I) sulphide. What is the percentage yield of the reaction?

(Relative atomic masses: S = 32.1, Cu = 63.5)

A 80.8%

B 84.8%

C 90.8%

D 94.8%

D

Unit 12

12.1: What is corrosion?

12.2: Corrosion of iron: rusting

(CDC guide: Corrosion of iron)

1 The chemical formula of rust is

A FeO.

B Fe2O3.

C FeOnH2O.

D Fe2O3nH2O.

D2 Which of the following iron nails would NOT rust after 3 days?

A3 The diagrams below represent four tests in an experiment designed to find out the necessary

conditions for rusting. Which diagram represents the most favorable conditions for rust to

appear on the nail?

C4 Iron corrodes more easily than other metals, but iron is still widely used in daily life. Which of

the following are possible reasons?

(1) Iron is strong.

(2) Iron is cheap.

(3) There are many methods used to prevent iron from corrosion.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D5 Which of the following statements are correct?

(1) Corrosion is the deterioration of a metal due to its reactions with substances in the

environment.

(2) Copper is more corrosion resistant than iron.

(3) Rusting is the corrosion of iron.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D6 Which of the following conditions are essential for rusting to occur?

(1) Oxygen

(2) High temperature

(3) Water

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

B

12.3: What factors speed up the rusting process?

12.4: To observe rusting using a rust indicator

(CDC guide: Factors that influence the rusting of iron)

1 The rate of rusting is the fastest when iron is connected to

A copper.

B silver.

C zinc.

D lead.

B2 Iron rusts faster in sea water than in distilled water because

A sea water is more acidic.

B sea water contains ionic substances.

C sea water contains more oxygen.

D sea water is more corrosive.

B3 Which iron nail in the test tubes shown below would rust most rapidly?

C4 Which iron nail in the test tubes shown below would rust most slowly?

C5 An iron nail is covered with water. Which of the following actions would NOT increase the

rate at which the nail corrodes?

A Adding some sodium sulphate to the water

B Adding some glucose to the water

C Attaching a copper wire to the nail

D Bubbling carbon dioxide into the water

B

6 In which of the following cases would the rusting of iron nail be fastest?

B7 In which of the following cases would the rusting of iron nail be slowest?

C8 Two experiments are set-up below to study the corrosion of an iron nail.

The rust indicator turns blue if the nail rusts. After a short time, blue colour will appear at

A both P and Q.

B neither P nor Q.

C P but not at Q.

D Q but not at P.

C9 The process of rusting is speeded up

(1) in the presence of sodium chloride solution.

(2) at a higher temperature.

(3) in the presence of dilute sulphuric acid.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D10 Which iron nail(s) below should be free from rusting after a long time?

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

A11 Car exhaust pipes rust rapidly because

(1) car exhaust gases are acidic.

(2) car exhaust gases contain water vapour.

(3) car exhaust pipes are subject to high temperature.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D12 In which of the following beakers would the iron NOT rust?

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

BDirections: Questions 13 and 14 refer to three different pairs of metal wires, which are placed

separately in petri dishes containing rust indicator solution.

13 If the iron wire rusts, what would be the colour of the rust indicator around the wire?

A Blue

B Orange

C Red

D Yellow

A14 Which of the following statements is / are correct?

(1) The iron wire in dish I corrodes readily.

(2) The iron wire in dish II corrodes readily.

(3) The iron wires in dish III do not corrode.

A (1) only

B (2) only

C (1) and (3) only

D (2) and (3) only

A

12.5: How to prevent rusting?

12.6: Socioeconomic implications of rusting

12.7: Which is the most suitable method to protect a particular iron article from

rusting?

(CDC guide: Methods used to prevent rusting)

1 Which of the following methods CANNOT prevent iron from rusting?

A Chromium-plating

B Wrapping a copper wire around the iron object

C Coating with oil

D Coating the surface with plastic

B2 Tin-plating can prevent iron from rusting because

A tin protects iron from air and water.

B tin corrodes instead of iron.

C tin is higher than iron in the reactivity series.

D tin is less reactive than iron.

A3 Tin-plated iron instead of galvanized iron is used to make food cans because

A tin corrodes less rapidly than zinc in air.

B tin and iron form an alloy which does not corrode.

C tin ions are non-toxic while zinc ions are toxic.

D tin is cheaper than zinc.

C4 The hull of a ship can be protected from corrosion by attaching a piece of metal to it.

The metal could be

A iron.

B potassium.

C tin.

D zinc.

D5 Which of the following methods can be used to prevent a bicycle chain from rusting?

A Coating with paint

B Coating with grease

C Attaching a piece of zinc to it

D Coating with plastic

B6 Which of the following methods can be used to prevent a sewing needle from rusting?

A Sacrificial protection

B Coating with oil

C Using alloys of iron

D Coating with paint

C7 Which of the following combinations is INCORRECT?

Iron article Method to prevent iron from rusting

A Bath tap Chromium-plating

B Fence Painting

C Door hinge Galvanization

D Underground pipeline Sacrificial protection

C8 Zinc coating can prevent iron from rusting because

A zinc is more reactive than iron.

B zinc is harder than iron.

C zinc forms a protective layer on the surface of iron.

D zinc loses electrons more readily than iron.

C9 Which of the following metals can offer both a protective layer and sacrificial protection to an

iron object?

A Zinc

B Silver

C Lead

D Copper

A10 Painting is NOT used to protect door hinges because

A paint is expensive.

B paint is easily scratched off.

C it is difficult to attach paint to door hinges.

D painting causes harm to environment.

B11 Which of the following CANNOT protect iron from rusting?

A Iron coated with tin

B Iron alloyed with chromium

C Iron covered with plastic

D Iron connected to tin

D12 Stainless steel is seldom used to make large objects because

A it is not strong enough.

B it is not malleable enough.

C it is too expensive.

D it is difficult to produce.

C13 Which of the following methods can prevent iron from rusting?

(1) Anodization

(2) Tin-plating

(3) Galvanization

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

C14 Which of the following processes could be used to slow down the corrosion of an iron nail?

(1) Painting the nail

(2) Coating a layer of zinc on the nail

(3) Putting the nail in distilled water

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

A15 Which of the following are commonly used as protective metals to prevent rusting of iron?

(1) Chromium

(2) Zinc

(3) Tin

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

D16 Which of the following are examples of sacrificial protection against rusting?

(1) Food cans coated with tin

(2) Underground iron pipes connected to bags of magnesium

(3) Hull of a ship connected to zinc blocks

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

C17 Which of the following processes CANNOT slow down the corrosion of an iron nail?

(1) Wrapping a copper wire around the iron nail

(2) Putting the iron nail in oil

(3) Attaching a piece of silver to the iron nail

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

B

12.8: Corrosion resistance of aluminium

(CDC guide: Corrosion resistance of aluminium & Anodization as a method to

enhance corrosion resistance of aluminium)

1 Why is aluminium a good choice for the manufacture of outdoor structures?

A Aluminium is easily reduced.

B Aluminium is not easily oxidized.

C Aluminium is easily reduced, but forms a protective coating.

D Aluminium is easily oxidized, but forms a protective coating.

D2 A food can corrodes quickly in sea water while a soft drink can does not. Which of the

following explanations is correct?

A Aluminium is more reactive than iron.

B Aluminium has a protective oxide layer on its surface.

C Aluminium is lighter than iron.

D A food can reacts with sodium chloride while a soft drink can does not.

B3 The process used to thicken the aluminium oxide layer on aluminium surface is known as

A galvanization.

B electroplating.

C anodization.

D reduction.

C4 Which of the following statements concerning the anodization of aluminium is INCORRECT?

A Aluminium object to be anodized is made the positive electrode.

B The negative electrode is made of aluminium sheet.

C Dilute sulphuric acid is used as an electrolyte.

D Oxygen is produced at the negative electrode.

D5 The experimental set-up of aluminium anodization is shown below.


Electrolyte Positive electrode Negative electrode

A Molten aluminium aluminium object X aluminium sheet Y

B Molten aluminium aluminium sheet Y aluminium object X

C Dilute sulphuric acid aluminium object X aluminium sheet Y

D Dilute sulphuric acid aluminium sheet Y aluminium object X

C6 Which of the following are the advantages of anodizing aluminium?

(1) It enables aluminium to be dyed readily.

(2) It makes aluminium stronger.

(3) It increases the corrosion resistance of aluminium.

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

B7 Which of the following substances are made of anodized aluminium?

(1) Milk bottle caps

(2) Window frames

(3) Bumpers of cars

A (1) and (2) only

B (1) and (3) only

C (2) and (3) only

D (1), (2) and (3)

A

Assertion-reason questions

Directions: Please refer to the following instructions:

A Both statements are true and the 2nd statement is a correct explanation of the 1st

statement.

B Both statements are true but the 2nd statement is NOT a correct explanation of

the 1st statement.

C The 1st statement is false while the 2nd statement is true.

D Both statements are false.

1st statement 2nd statement

1 The demand for metals is ever

increasing.

The world population increases

continuously.

A

2 Aircraft bodies are made of aluminium. Aluminium has a low density. A

3 Titanium is used in making space

shuttles.

Titanium is light and strong. A

4 All copper exists as a free element in the

Earth’s crust.

Copper has been used by mankind since

ancient times.

C

5 Aluminium was used earlier than iron in

the history of mankind.

Aluminium is more abundant than iron in

the Earth’s crust.

C

6 Soft drink cans are usually recycled. Recycling of metals can help to reduce

the pollution problem.

A

7 Electrolysis is used to extract sodium

from molten sodium ore.

It is very difficult to reduce sodium ore

by using other methods.

A

8 When lead is heated in the air, a white

solid is formed on cooling.

Lead (II) oxide is yellow when it is hot

and white when it is cool.

D

9 When steam is passed over calcium,

hydrogen and calcium oxide are

produced.

Calcium reacts with water readily. B

10 Zinc reacts less vigorously with dilute

hydrochloric acid than iron.

Zinc is less reactive than iron. D

11 Lead does not react with dilute

hydrochloric acid readily.

Lead is lower than iron in the reactivity

series.

B

12 When magnesium is added to dilute

sulphuric acid, hydrogen gas is evolved.

Magnesium atoms donate electrons to

hydrogen ions and thus hydrogen

molecules are formed.

A

13 The electrical conductivity of copper is

poorer than iron.

Copper is lower than iron in the

reactivity series.

C

14 Aluminium was discovered later than

copper.

Aluminium is more abundant than

copper in the Earth’s crust.

B

15 Aluminium is more ractive than calcium. Aluminium forms positive ion more

easily than calcium.

D

16 Alminium can displace iron form iron

(II) nitrate solution.

Aluminium is more reative than iron. A

17 When zinc is added to copper (II)

sulphate solution, the blue colour of the

solution fades.

Zinc sulphate is soluble in water. B

18 When copper is placed in silver nitrate

solution, a brown deposit appears.

Silver is displaced from silver nitrate

solution by copper.

C

19 Lead can displace iron from iron (II)

sulphate solution.

Lead is more reactive than iron. D

20 When sodium is added to zinc choride

solution, a layer of zinc would form on

the surface of sodium.

Sodium is higher than zinc in the

reactivity series.

C

21 Copper (II) oxide can be reduced by

heating with magnesium.

Magnesium has a higher affinity for

oxygen than copper.

A

22 Carbon is more commonly used to Carbon is cheaper than calcium. A

reduce copper (II) oxide than calcium.

23 Comparing to more reactive metals, it is

more difficult to extract less reactive

metals from their ores.

More reactive metals lose electrons more

readily.

C

24 Copper has been used by humans earlier

than iron.

Copper is more easily extracted than

iron.

A

25 It is impossible to find out the absolute

masses of atoms.

An atom is usually light in mass. C

26 24.3 g of magnesium can form 2 moles

of magnesium ions.

A magnesium atom loses two electrons

to form a magnesium ion.

C

27 The mass of carbon in carbon dioxide is

half that of oxygen.

In 1 mole of carbon dioxide, there are 1

mole of carbon atoms and 2 moles of

oxygen atoms.

C

28 The mass of 1 mole of carbon monoxide

is the same as the mass of 1 mole of

nitrogen.

At room temperature and pressure, both

carbon monoxide and nitrogen are gases.

B

29 The volume of 1 mole of carbon is

different from that of 1 mole of sulphur.

1 mole of carbon contains the same

number of atoms as 1 mole of sulphur.

B

30 At room temperature and pressure, the

volume of 10.0 g of steam is the same as

that of 10.0 g of water.

10.0 g of steam contain the same number

of molecules as 10.0 g of water.

C

31 2.0 g of hydrogen react with 1.0 g of

oxygen to give 2.0 g of water.

Two moles of hydrogen react with one

mole of oxygen molecules to give two

moles of water molecules.

C

32 At room temperature and pressure, the

volume occupied by 1 mole of sulphur

atoms is twice that occupied by 1 mole

of oxygen atoms.

The number of atoms contained in one

mole of sulphur atoms is twice that

contained in 1 mole of oxygen atoms.

D

33 1 mole of aluminium atoms can form 3

moles of aluminium ions.

An aluminium atom loses three electrons

to form an aluminium ion.

C

34 An iron nail kept in vacuum will not rust

at all.

Rusting only occurs when both oxygen

and water are present.

A

35 An iron nail rusts more rapidly in sea

water than in tap water.

Ionic substances in sea water speed up

the rusting of iron.

A

36 Tin-plating instead of galvanization is

applied to iron food cans.

Tin is less reactive than zinc. B

37 The negative terminal of a car battery

can be connected to the body of a car to

prevent corrosion.

The battery supplies electrons to the car

body to prevent it from being oxidized.

A

38 Iron is commonly protected from

corrosion by coating it with a layer of

calcium.

Calcium can provide sacrificial

protection to iron.

C

39 When an iron nail wrapped with a copper

wire is left in air for a long period of

time, the iron nail does not corrode.

Copper prevents iron from rusting by

sacrificial protection.

D

40 Lead can be used as a sacrificial metal to

prevent iron from rusting.

Lead is lower than iron in the reactivity

series.

C

41 When an iron nail wrapped with a zinc

wire is placed in a test tube containing

tap water and a few drops of indicator, a

blue colour can be observed after a few

days.

Zinc facilitates the rusting of the iron

nail.

D

42 Aluminium is not a reactive metal. Aluminium is corrosion resistant. C

43 When a mixture of iron(III) oxide

powder and aluminium powder is

ignited, iron and aluminium oxide form.

Aluminium is more corrosion resistant

than iron.

B

44 Anodization makes aluminium stronger. Anodization of aluminium can increase

its corrosion resistance.

C

45 Anodization is a method used to increase

the strength of aluminium.

By anodization, a thick oxide layer is

formed on the surface of aluminium.

C

Structured questions

1 The table below shows information about four different metals ― A, B, C and D.

Metal Cost Corrosion

resistance

Heat

conductivity

Mechanical

strength

Density

A Low Low Medium Medium Low

B High High Good High High

C Low Medium Medium High Medium

D Medium Medium Good Medium Medium

Which metal is the most suitable for making

a) medal;

b) a gate; and

c) the metal base of a hot pot?

State TWO reasons for your choice in each case.

(9 marks)

Answer:

1 a) B (1)

Any TWO of the following: (1 2)

High corrosion resistance

High mechanical strength

High density

b) C (1)


Cheap

High mechanical strength

Medium density

c) D (1)

Medium price (1)

Good conductivity of heat (1)

2 Consider the following metals:

Aluminium, tin, copper, lead, zinc and titanium

For each of the tasks listed below, choose ONE metal which is best for accomplishing the

task. Explain your choice in each case.

a) Making space shuttles

b) Protecting food cans from rusting

c) Making soft drink cans

(6 marks)

Answer:

2 a) Titanium (1)

Very strong / light (1)

b) Tin (1)

Non-poisonous (1)

c) Aluminium (1)

High corrosion resistance / light (1)

3 The figure shows a piece of electrical wire.

a) Which metal is the most suitable for making electrical wires?

b) Suggest TWO essential properties of that metal which make it suitable for making

electrical wires.

c) Account for the properties mentioned in (b) in terms of metallic bond.

d) Explain with equations, if any, what will happen if this wire is put into

i) dilute hydrochloric acid; and

ii) silver nitrate solution.

(8 marks)

Answer:

3 a) Copper (1)

b) Very good conductor of electricity (1)

Very ductile (1)

c) Copper is a good conductor of electricity because it has mobile electrons. (1)

Copper is ductile because when the metal is pulled, the copper atom layers

can slide over each other but are still bound together by the sea of electrons. (1)

d) i) No observable change as copper has a very low reactivity. (1)

ii) The solution turns blue. / Grey deposits form. / The copper wire dissolves. (1)

Cu(s) + 2AgNO3(aq) Cu(NO3)2(aq) + 2Ag(s) (1)

or Cu(s) + 2Ag+(aq) Cu2+(aq) + 2Ag(s)

4 The table below lists some information about three metals A, B and C.

Metal A B C

Atomic number 12 20 ―

Heating in air Burns with bright

light

Burns with a brick-red flame No observable

change

Reaction with

water

No observable

change

Gas bubbles are given off,

slowly at first but becomes

faster after some time

No observable

change

a) To which group in the periodic table do A and B belong?

b) Metal A does not react with water but reacts with steam readily.

i) Write a chemical equation for the reaction between A and steam.

ii) Draw an electron diagram for the solid product formed in (i), showing electrons

in the outermost shells only.

c) i) Write an equation for the reaction between B and water.

(An ionic equation will NOT be accepted for this question.)

ii) Draw an electron diagram for the gaseous product formed in the reaction.

iii) Suggest an explanation for the observation made when B reacts with water.

iv) Draw a labelled diagram of the set-up for carrying out the reaction between B

and water, with the collection of the gaseous product.

d) Suggest what C might be.

e) Explain, in terms of electronic structure, why B is more reactive than A.

(12 marks)

Answer:

4 a) Group II (1)

b) i) Mg(s) + H2O(g) MgO(s) + H2(g) /

A(s) + H2O(g) AO(s) + H2(g) (1)

ii)

(1)

c) i) Ca(s) + 2H2O(l) Ca(OH)2(s) + H2(g) /

B(s) + 2H2O(l) B(OH)2(s) + H2(g) (1)

ii)

(1)

iii) The calcium metal is covered by a layer of calcium oxide. (1)

Reaction between calcium and water only starts when the oxide layer dissolves. (1)

iv)

(2)

d) Silver / gold / platinum (1)

e) An atom of B has one more occupied electron shell than an atom of A. The outermost

shell electrons of an atom of B are further away from the nucleus than those of an atom

of A. In an atom of B, the attraction between the outermost shell electrons and the

nucleus is weaker. (1)

Therefore, B loses electrons more readily than A. (1)

5 Results of some reactions of four metals A, B, C and D are shown below:

Reaction Result

(i) A(s) + HCl(aq) No reaction

(ii) B(s) + HCl(aq) Reacts steadily to give hydrogen

(iii) A(s) + O2 (g) An oxide is formed when heated

(iv) D(s) + O2 (g) No reaction when heated

(v) B(s) + H2O (g) Reacts slowly with steam

(vi) C(s) + H2O (g) Reacts vigorously with steam

a) Arrange the four metals in descending order of reactivity. Explain briefly.

b) Another metal E reacts with dilute hydrochloric acid to give hydrogen.

The solution of a compound of E also shows the following reaction:

B(s) + E2+(aq) B2+(aq) + E(s)

Where would you place E in the reactivity series among A, B, C and D?

Explain briefly.

(7 marks)

Answer:

5 a) C > B > A > D (1)

From reactions (v) and (vi), it can be concluded that C is more reactive than B

because C reacts vigorously with steam while B reacts slowly with steam. (1)

From reactions (i) and (ii), it can be concluded that B is more reactive than A

because B reacts with dilute hydrochloric acid but A does not. (1)

From reactions (iii) and (iv), it can be concluded that A is more reactive than D

because oxide of A is formed on heating while there is no reaction for D. (1)

b) E is more reactive than A because E reacts with dilute hydrochloric acid but A

does not. (1)

E is less reactive than B because B can displace E from a solution of compound of E.(1)

Thus, E should be placed between B and A in the reactivity series. (1)

6 a) For each of the following experiments, state ONE observable change and write a

chemical equation for the reaction involved.

i) Magnesium is put into dilute hydrochloric acid.

ii) Sodium is heated in a Bunsen flame.

iii) Lead(II) oxide is heated with carbon powder.

iv) Zinc is put into copper(II) sulphate solution.

b) Explain why there is NO reaction in the following experiments.

i) Lead is put into dilute sulphuric acid.

ii) Calcium oxide is heated with carbon powder.

iii) Copper is put into magnesium nitrate solution.

(14 marks)

Answer:

6 a) i) Magnesium dissolves. / Gas bubbles are given off. (1)

Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g) (1)

ii) A golden yellow flame is observed. / A white smoke is formed. (1)

4Na(s) + O2(g) 2Na2O(s) (1)

iii) The yellow solid turns orange. / A silvery solid is formed. (1)

2PbO(s) + C(s) 2Pb(s) + CO2(g) (1)

iv) Zinc dissolves. / A brown solid deposits. / The blue colour of the solution fades

gradually. (1)

Zn(s) + CuSO4(aq) Cu(s) + ZnSO4(aq) (1)

b) i) Insoluble lead(II) sulphate is formed on the surface of lead. (1)

It prevents further reaction. (1)

ii) Calcium oxide is very stable. (1)

It cannot be reduced by carbon. (1)

iii) Copper is less reactive than magnesium. (1)

Copper cannot displace magnesium from solution of magnesium compounds. (1)

7 Sodium can be used as a drying agent to remove trace of water in organic solvents. Sodium

is first drawn into a wire and placed in a bottle of organic solvent.

a) Explain, with the help of a chemical equation, why sodium can be used as a drying

agent.

b) Explain why sodium can be drawn into wire in terms of its structure.

c) When sodium was drawn into a wire, it appears shiny at first but turns grey after

exposed to air. Explain this observation with a relevant equation.

d) Suggest ONE potential hazard of using this method in drying organic solvents.

(7 marks)

Answer:

7 a) Sodium reacts with water to give sodium hydroxide and hydrogen. (1)

2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g) (1)

b) The atoms in sodium are packed in layers. (1)

When the metal is pulled into thin wires, the atom layers can slide over each other but

are still bound together by the sea of electrons. (1)

c) When sodium is freshly drawn, new surface is exposed as shiny surface. But it is

rapidly oxidized by the air to form oxide. (1)

4Na(s) + O2(g) 2Na2O(s) (1)

d) Sodium may react explosively with other substances, such as water, in the process of

preparation and disposal. (1)

8 The reactivity of metals can be determined by the reaction between metal and acid.

Five different metals, calcium, tin, zinc, copper and nickel are added to dilute hydrochloric

acid respectively. The gas produced is collected by displacement of water. The height of

gas collected in the first 30 seconds in each case is measured.

The results are shown in the following table.

Metal calcium tin zinc copper nickel

Height (cm) of gas collected

in the first 30 seconds

5.5 1 4.5 0 2.5

a) Write a chemical equation for the reaction between zinc and dilute hydrochloric acid.

b) Suggest a test for the gas evolved.

c) Determine the reactivity series in descending order from the results provided.

d) Explain why the reactivity of sodium CANNOT be determined by this method.

e) Explain why it is NOT suitable to use dilute sulphuric acid to replace dilute

hydrochloric acid in this experiment.

f) Another metal was tested and the result was as follows:

Metal X

Height (cm) of gas collected in the first 30 seconds 5

i) From the result obtained, rewrite the reactivity series.

ii) Suggest what metal X might be.

(9 marks)

Answer:

8 a) Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g) (1)

b) Hydrogen gas gives a ‘pop’ sound (1)

with a burning splint. (1)

c) Calcium > zinc > nickel > tin > copper (1)

d) Sodium reacts with acids explosively. (1)

e) When calcium reacts with dilute sulphuric acid, insoluble calcium sulphate will form

on the surface of calcium. (1)

This prevents the metal from further reaction. (1)

f) i) Calcium > metal X > zinc > nickel > tin > copper (1)

ii) Magnesium / aluminium (1)

9 This following table shows the densities of two Group I metals.

Metal Density (g cm-3)

Lithium (Li) 0.53

Rubidium (Rb) 1.53

Density of water = 1.0 g cm-3

a) i) Suggest TWO observable differences when lithium and rubidium are added into a

water trough separately.

ii) Account for the differences.

iii) Write a chemical equation for the reaction between rubidium and water.

b) Rubidium is stored in paraffin oil in a bottle with suitable hazard warning labels.

i) Why should rubidium be stored in paraffin oil?

ii) Draw ONE hazard warning label which should appear on the bottle containing

rubidium.

(8 marks)

Answer:

9 a) i) Rubidium will sink in water but lithium will float on water. (1)

Rubidium reacts more vigorously than lithium. (1)

ii) Rubidium is denser than water and lithium is less dense than water. (1)

The outermost shell electron in a rubidium atom is further away from the nucleus

than that in a lithium atom. This results in a weaker attraction between the nucleus

and the outermost shell electron in a rubidium atom. (1)

Therefore, rubidium loses electrons more readily than lithium. (1)

iii) 2Rb(s) + 2H2O(l) 2RbOH(aq) + H2(g) (1)

b) i) It prevents rubidium from reacting with moisture and oxygen in air. (1)

ii) Explosive (1)

or flammable

10 A metal M reacts with very dilute nitric acid to form a solution B and a gas C but M has no

reaction with steam. When M is heated with a Bunsen flame, it gives a solid D. The solid is

orange when it is hot and yellow when it is cold.

a) Suggest what M, B, C and D might be.

b) Suggest a test for gas C.

c) Write chemical equation(s) for the extraction of metal M from its sulphide.

d) i) Describe what will be observed when a piece of metal M is added to silver

nitrate

solution.

ii) Write an ionic equation for the reaction involved.

(11 marks)

Answer:

10 a) M: lead (1)

B: lead(II) nitrate solution (1)

C: hydrogen (1)

D: lead(II) oxide (1)

b) It gives a ‘pop’ sound (1)

with a burning splint. (1)

c) 2PbS(s) + 3O2(g) 2PbO(s) + 2SO2(g) (1)

2PbO(s) + C(s) 2Pb(s) + CO2(g) (1)

d) i) Lead dissolves. / M dissolves. (1)

A grey solid deposits. (1)

ii) Pb(s) + 2Ag+(aq) Pb2+(aq) + 2Ag(s) (1)

11 The following table shows information on extraction of metals of the reactivity series.

Metal Extraction Method Ease of extraction

K

Method A

Difficult

Easy

Na

Ca

Mg

Al

Zn Carbon reduction

Fe

Pb

Cu

HgHeating the ore

Ag

a) Briefly describe the method A used in the extraction of reactive metals.

b) Write a chemical equation for extracting copper from copper(II) oxide by

carbon reduction.

c) i) Name another reducing agent that can be used instead of carbon to reduce

copper(II) oxide.

ii) Write a chemical equation for the reaction involved.

d) Write a chemical equation for obtaining silver from its oxide by heating alone.

e) Explain whether a reaction occurs in each of the following cases. State ONE

observation if a reaction occurs.

i) Put zinc into silver nitrate solution

ii) Put copper into magnesium nitrate solution

f) State the relationship between the year of discovery and the ease of extraction for a

metal.

(10 marks)

Answer:

11 a) Electrolysis of the molten ores of metals (1)

Metal will be obtained at the negative electrode. (1)

b) 2CuO(s) + C(s) 2Cu(s) + CO2(g) (1)

c) i) Hydrogen / carbon monoxide (1)

ii) CuO(s) + H2(g) Cu(s) + H2O(l) (1)

or CuO(s) + CO (g) Cu(s) + CO2(g)

d) 2Ag2O(s) 4Ag(s) + O2(g) (1)

e) i) A reaction occurs because zinc is more reactive than silver. (1)

Zinc dissolves. / A grey solid deposits. (1)

ii) No reaction occurs because copper is less reactive than magnesium. (1)

f) The easier the extraction of a metal, the earlier the metal is discovered. (1)

12 The following metals are arranged in the order of decreasing reactivity.

Metal a > metal b > metal c > iron > metal d > metal e > metal f

Based on the information given above, answer the following questions.

a) Which metal is most likely to tarnish rapidly in air? Explain your answer.

b) Which metal is most likely to be found free in nature? Explain your answer.

c) Would you expect metal d to react with cold water? Explain your answer.

d) Suggest how metal a can be extracted from its ore.

e) What would be formed when the oxide of metal d is heated with coke?

f) Suggest an experiment to show that metal b is more reactive than iron.

g) Can we store the solution of nitrate of metal c in a container made of metal d?

Explain your answer.

(12 marks)

Answer:

12 a) Metal a (1)

Because it is the most reactive metal and thus reacts rapidly with oxygen in air to form

an oxide layer on the metal surface. (1)

b) Metal f (1)

Because it is the least reactive metal and thus does not form stable compounds readily.

(1)

c) No. (1)

Iron has no reaction with cold water and metal d is less reactive than iron. (1)

d) Electrolysis of its molten ore (1)

e) Metal d is formed. (1)

f) Add metal b to iron(II) sulphate solution. (1)

Metal b can displace iron from iron(II) sulphate solution. (1)

g) Yes. (1)

Since metal d is less reactive than metal c, no displacement reaction occurs. (1)

13 A student performs several experiments to determine the order of reactivity of five metals(P,

Q, R, S and T). The results are shown in the table below.

ExperimentMetal

P Q R S T

Reaction with

water

Reacts

readily

No reaction No reaction Reacts

vigorously

No reaction

Reaction with

steam

Reacts

readily

No reaction Reacts very

slowly

Reacts

vigorously

No reaction

Reaction with

dilute

hydrochloric acid

Reacts

readily

No reaction Reacts

slowly

Reacts

explosively

No reaction

Heating the metal

oxide with carbon

No reaction Metal Q

obtained

Metal R

obtained

No reaction Metal T

obtained

Displacement

reaction

T displaces Q from the solution of nitrate of Q

a) Arrange the metals in order of reactivity, starting with the most reactive one.

Explain your answer briefly.

b) i) Suggest what metal P might be.

ii) Write a chemical equation for the reaction between metal P and dilute

hydrochloric acid.

iii) State TWO observations when metal P is heated in air.

c) i) Suggest what metal S might be.

ii) Write a chemical equation for the reaction between metal S and water.

iii) Suggest how metal S can be extracted from its ore.

d) i) During reactions, metal R forms R2+ ions. Write a chemical equation for the

reaction between metal R and steam.

ii) Draw electron diagrams of the products formed in (i) above, showing electrons

in

the outermost shells only.

e) Metal Q forms an oxide with a chemical formula of Q2O.

i) Suggest what metal Q might be.

ii) Would there be any reaction between zinc and the solution of nitrate of Q?

Write an ionic equation for the reaction, if any.

(18 marks)

Answer:

13 a) S > P > R > T > Q (1)

P and S are more reactive than Q, R, and T because P and S react with water while Q,

R and T do not. (1)

S is more reactive than P as S reacts more vigorously with water than P. (1)

R is more reactive than Q and T because R reacts slowly with dilute hydrochloric acid

while Q and T show no reaction. (1)

T is more reactive than Q because T displaces Q from the solution of nitrate of Q. (1)

b) i) Calcium (1)

ii) Ca(s) + 2HCl(aq) CaCl2(aq) + H2(g) (1)

iii) It burns with a brick-red flame. (1)

A white solid is formed. (1)

c) i) Sodium / potassium (1)

ii) 2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g) (1)

or 2K(s) + 2H2O(l) 2KOH(aq) + H2(g)

iii) Electrolysis of its molten ore (1)

d) i) R(s) + H2O(g) RO(s) + H2(g) (1)

ii)

(1)

(1)

e) i) Silver (1)

ii) Yes (1)

Zn(s) + 2Ag+(aq) Zn2+(aq) + 2Ag(s) (1)

14 The following tables record the results of some reactions of four different metals and their

oxides.

Metal

Reaction

W X Y Z

Adding dilute

hydrochloric

acid

Very dangerous!

Never attempt

No observable

change

Bubbles given

off

Bubbles given

off

Adding copper

(II) nitrate

solution

Bubbles given

off

No observable

change

Metal dissolves,

a brown solid

deposits

Metal dissolves,

a brown solid

deposits

Heating the

oxide alone

No observable

change

A silvery solid

is formed

No observable

change

No observable

change

Heating the

oxide with

carbon

No observable

change

― A silvery grey

solid is formed

No observable

change

a) Arrange the four metals in descending order of reactivity. Explain your answer briefly.

b) If Z burns in air with a bright light, suggest what metal Z might be and write a

chemical equation for its reaction with dilute hydrochloric acid.

c) Draw electron diagrams of the products formed in (b), showing electrons in the

outermost shells only.

d) Explain the observation, with the help of an equation, when metal W is added to

copper(II) nitrate solution.

e) Suggest and explain another observable change when metal Y is added to copper(II)

nitrate solution.

(12 marks)

Answer:

14 a) W > Z > Y > X (1)

Only the oxide of X can be reduced easily by heating alone, therefore X is the least

reactive. (1)

Y can be obtained by carbon reduction of its oxide, but W and Z cannot. It means that

W and Z are more reactive. (1)

W is the most reactive since only W reacts vigorously with dilute hydrochloric acid. (1)

b) Magnesium (1)

Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g) (1)

c) MgCl2:

(1)

H2:

(1)

d) W is so reactive that it reacts with water instead of displacing copper from copper(II)

nitrate solution. (1)

2W(s) + 2H2O(l) 2WOH(aq) + H2(g) (1)

e) The blue colour of the solution fades (1)

as the concentration of copper(II) ions in the solution decreases. (1)

15 The results of a series of displacement reactions are given in the table below.

Salt solution

Metal

Nitrate of X Lead(II)

nitrate

Iron(II)

nitrate

Silver nitrate

X ― Reaction

occurs

Reaction

occurs

Reaction

occurs

Lead No

observable

change

― No observable

change

Reaction

occurs

Iron No

observable

change

Reaction

occurs

― Reaction

occurs

Silver No

observable

change

No observable

change

No observable

change

―

a) What is displacement reaction?

b) List TWO observable changes when X is put into iron(II) sulphate solution.

c) Based on the information given above, arrange the metals in descending order of

reactivity. Briefly explain your answer.

d) Chromium should be placed between X and iron in reactivity series. Suppose you are

provided with chromium(III) nitrate solution, describe an experiment to show this.

e) Write an ionic equation for the reaction between iron and silver nitrate solution.

(10 marks)

Answer:

15 a) The reaction in which a more reactive metal displaces a less reactive metal

from a solution of the compound of the less reactive metal. (1)

b) Any TWO of the following: (1 2)

Metal X dissolves.

A grey solid deposits.

The green colour of the solution fades.

c) X > iron > lead > silver (1)

X is the most reactive since it can displace all other three metals from solutions of

their salts. (1)

Iron is more reactive than lead and silver because it can displace lead and silver

from solutions of their salts. (1)

Silver is the least reactive as it cannot displace any metal. (1)

d) Put X and iron into two separate test tubes each containing chromium(III) nitrate

solution. (1)

X can displace chromium from chromium(III) nitrate solution but iron cannot (1)

It shows that chromium is between X and iron in the reactivity series.

e) Fe(s) + 2Ag+(aq) Fe2+(aq) + 2Ag(s) (1)

16 a) Calculate the number of moles of the following substances.

i) 1.20 1025 sodium atoms

ii) 22.8 g of nitrogen dioxide molecules

iii) 4.80 1023 formula units of copper(II) carbonate

iv) 13.2 g of hydrated magnesium sulphate (MgSO47H2O)

b) Calculate the masses of the following substances.

i) 2.00 moles of sodium hydroxide

ii) 1.90 1024 ethane molecules (C2H6)

iii) 0.400 mole of hydrated sodium carbonate (Na2CO310H2O)

iv) 3.90 1022 argon atoms

(Relative atomic masses: H = 1.0, C = 12.0, N = 14.0, O = 16.0, Na = 23.0,

Mg = 24.3, S = 32.1, Ar = 40.0; Avogadro constant = 6.02 1023 mol-1)

(8 marks)

Answer:

16 a) i) 1.20 1025 ÷ 6.02 1023 mol-1 = 19.9 mol (1)

ii) 22.8 g ÷ (14.0 + 2 16.0) g mol-1 = 0.496 mol (1)

iii) 4.80 1023 ÷ 6.02 1023 mol-1 = 0.797 mol (1)

iv) 13.2 g ÷ [24.3 + 32.1 + 4 16.0 + 7 (2 1.0 + 16.0)] g mol-1

= 0.0536 mol (1)

b) i) 2.00 mol (23.0 + 1.0 + 16.0) g mol-1 = 80.0 g (1)

ii) (1.90 1024 ÷ 6.02 1023) mol (2 12.0 + 6 1.0) g mol-1 = 94.7 g (1)

iii) 0.400 mol [2 23.0 + 12.0 + 3 16.0 + 10 (2 1.0 + 16.0)] g mol-1 = 114 g

(1)

iv) (3.90 1022 ÷ 6.02 1023) mol 40.0 g mol-1 = 2.59g (1)

17 a) In 67.5 g of hydrated aluminium sulphate Al2(SO4)36H2O, calculate

i) the number of moles of aluminium ions present;

ii) the number of moles of water molecules present;

iii) the number of sulphur atoms present;

iv) the number of oxygen atoms present; and

v) the number of ions present.

b) When 1.96 g of metal M are completely changed to ions, 3.61 1022 electrons are

released. The relative atomic mass of M is 65.4.

i) What is the number of moles of 1.96 g of M?

ii) What is the number of moles of electrons released?

iii) What is the charge on an ion of M?

(Relative atomic masses: H = 1.0, O = 16.0, Al = 27.0, S = 32.1; Avogadro

constant = 6.02 1023 mol-1)

(9 marks)

Answer:

17 a) i) Number of moles of Al2(SO4)36H2O

= 67.5 g ÷ [ 2 27.0 + 3 (32.1 + 4 16.0) + 6 (2 1.0 + 16.0)] g mol-1

= 0.150 mol (1)

Number of moles of aluminium ions = 2 0.150 mol = 0.300 mol (1)

ii) Number of moles of water molecules = 6 0.150 mol = 0.900 mol (1)

iii) Number of sulphur atoms = 3 0.150 mol 6.02 1023 mol-1

= 2.71 1023 (1)

iv) Number of oxygen atoms = 18 0.150 mol 6.02 1023 mol -1

= 1.63 1024 (1)

v) Number of ions = 5 0.150 mol 6.02 1023 mol-1 = 4.52 1023 (1)

b) i) Number of moles of M = 1.96 g ÷ 65.4 g mol-1 = 0.0300 mol (1)

ii) Number of moles of electrons = 3.61 1022 ÷ 6.02 1023 mol-1

= 0.0600 mol (1)

iii) The charge on an ion of M = 0.0600 mol ÷ 0.0300 mol = +2 (1)

18 a) 2.70 g of a metal M combines with 2.40 g of oxygen to form an oxide with the formula

M2O3. What is the relative atomic mass of M?

b) A crystalline salt (MCl36H2O) is found to contain 40.5% by mass of water of

crystallization. Calculate

i) the formula mass of the hydrated salt; and

ii) the relative atomic mass of the metal M.

(Relative atomic masses: H = 1.0, O = 16.0, Cl = 35.5)

(6 marks)

Answer:

18 a) Let Mr be the relative atomic mass of metal M.

Number of moles of M : number of moles of O = 2 : 3 = : (1)

Mr = 27.0 (1)

or Mass of M in oxide : Mass of oxygen in oxide

= 2.70 : 2.40 = 2Mr : 3 16.0

Mr = 27.0

b) i) Formula mass of the hydrated salt = (6 18.0) ÷ 0.405 (1)

= 267 (1)

ii) Relative atomic mass of metal M = 267 − (6 18.0 + 3 35.5)

(1)

= 52.5 (1)

19 a) 10.1 g of hydrated calcium chloride (CaCl2nH2O) gives 5.00 g of water on strong

heating. Find the value of n.

b) A hydrated salt of copper contains 63.9% by mass of the anhydrous salt. The anhydrous

salt has the following percentage composition by mass: copper 39.8%; sulphur 20.1%;

oxygen 40.1%. Find the empirical formula of the hydrated salt.

(Relative atomic masses: H = 1.0, O = 16.0, S = 32.1, Cl = 35.5, Ca = 40.1, Cu =

63.5)

(8 marks)

Answer:

19 a) Number of moles of CaCl2 : Number of moles of H2O = 1 : n

Number of moles of CaCl2 = 5.10 g ÷ (40.1 + 2 35.5) g mol-1

= 0.0459 mol (1)

Number of moles of H2O = 5.00 g ÷18.0 g mol-1 = 0.278 mol (1)

1 : n = 0.0459 : 0.278

n = 6 (1)

b) Suppose there are 100 g of anhydrous salt.

Copper Sulphur Oxygen

Mass of element 39.8 g 20.1 g 40.1 g

Number of moles

of atoms that

combine

39.8 g ÷ 63.5 g mol-1

= 0.627 mol

20.1 g ÷ 32.1g mol-1

= 0.626 mol

40.1 g ÷ 16.0 g mol-1

= 2.51 mol

Simplest whole

number ratio of

atoms

0.627 ÷ 0.626 = 1 0.626 ÷ 0.626 = 1 2.51 ÷ 0.626 = 4

So the empirical formula of the anhydrous salt is CuSO4.

Formula mass of the hydrated salt = (63.5 + 32.1 + 4 16.0) ÷ 0.639 = 250 (1)

Let the empirical formula of the hydrated salt be CuSO4nH2O.

63.5 + 32.1 + 4 16.0 + 18n = 250 (1)

n = 5

The empirical formula of the hydrated salt is CuSO45H2O. (1)

20 The following diagram shows the set-up used in an experiment to determine the empirical

formula of a black copper oxide.

Town gas (main constituents being carbon monoxide and hydrogen) was passed over the

oxide before heating. The black copper oxide was reduced to copper in the experiment.

Heating was stopped after some time. Town gas was passed over the copper until it was cold.

The results are as follows:

Mass of tube = 25.20 g

Mass of tube and copper oxide = 27.78 g

Mass of tube and copper formed = 27.26 g

a) Why was town gas passed over the chemical before and after the experiment?

b) State an expected observation in this experiment.

c) Suggest ONE test to show that a metal is formed in this experiment.

d) Write appropriate equations to account for the chemical change of the copper oxide.

e) Calculate the number of moles of copper formed.

f) Calculate the number of moles of oxygen present in the copper oxide.

g) From the results of (e) and (f), determine the empirical formula of the copper oxide.

h) List TWO potential hazards of this experiment.

(Relative atomic masses: O = 16.0, Cu = 63.5)

(11 marks)

Answer:

20 a) Before experiment: To flush the air out because a mixture of town gas and air may

explode on ignition. (1)

After experiment: To prevent oxidation of the copper by air again. (1)

b) The black oxide changed to reddish brown metal. (1)

c) The metal obtained can conduct electricity. (1)

d) CuO(s) + CO(g) Cu(s) + CO2(g) (1)

CuO(s) + H2(g) Cu(s) + H2O(l) (1)

e) Number of moles of copper formed = (27.26 − 25.20) g ÷ 63.5 g mol-1

= 0.0324 mol (1)

f) Number of moles of oxygen in the oxide = (27.78 − 27.26) g ÷ 16.0 g mol-1

= 0.0325 mol (1)

g) Mole ratio of copper to oxygen = 0.0324 : 0.0325 = 1 : 1

So the empirical formula of the copper oxide is CuO. (1)

h) Town gas is toxic (carbon monoxide) and explosive (hydrogen). (1, 1)

21 The following set-up was used to determine the empirical formula of an oxide of cobalt

(Co).

The experimental results were as follows:

(1) Mass of crucible + lid = 20.49 g

(2) Mass of crucible + lid + cobalt = 23.13 g

(3) Mass of crucible + lid + oxide of cobalt = 24.09 g

a) Give TWO reasons why the crucible should be half covered with the lid during

heating, as shown in the diagram.

b) Calculate the empirical formula of the oxide of cobalt.

c) Cobalt-60 is widely used as a medical and industrial radiation source.

Complete the following information for a 60Co atom.

Number of protons Number of neutrons

(i) (ii)

(Relative atomic masses: O = 16.0, Co = 58.9)

(7 marks)

Answer:

21 a) To ensure there is enough oxygen to react with cobalt. (1)

To prevent the loss of the oxide formed. (1)

b)

Cobalt Oxygen

Number of moles of

atoms that combine

2.64 g ÷ 58.9 g mol-1

= 0.0448 mol

0.960 g ÷ 16.0 g mol-1

= 0.0600 mol (1)

Simplest ratio of atoms 0.0448 mol ÷ 0.0448 mol

= 1

0.0600 mol ÷ 0.0448 mol

= 1.34 (1)

Simplest whole number

ratio of atoms3 4 (1)

The empirical formula of the cobalt oxide is Co3O4.

c) i) 27 (1)

ii) 33 (1)

22 a) Both nitrogen and fluorine are non-metals. Draw electron diagrams of the following

molecules:

i) a nitrogen molecule

ii) a fluorine molecule

b) Nitrogen can form a fluoride with relative molecular mass of 66.0. The compound

contains 42.4% of nitrogen by mass.

i) Deduce the molecular formula of the compound.

ii) Draw an electron diagram of the compound, showing electrons in the outermost

shells only.

(Relative atomic masses: N = 14.0, F = 19.0)

(6 marks)

Answer:

22 a) i)

(1)

ii)

(1)b) i) Suppose there are 100 g of the fluoride, so there are 42.4 g of nitrogen and 57.6 g

of fluorine.

Nitrogen Fluorine

Number of moles of

atoms that combine

42.4 g ÷ 14.0 g mol-1

= 3.03 mol

57.6 g ÷ 19.0 g mol-1

= 3.03 mol (1)

Simplest ratio of

atoms

3.03 mol ÷ 3.03 mol = 1 3.03 mol ÷ 3.03 mol = 1 (1)

\The empirical formula of the fluoride is NF.

Let (NF)n be the molecular formula of the fluoride.

Relative molecular mass of the fluoride = n (14.0 + 19.0) = 66.0

\n = 2 (1)

\The molecular formula of the fluoride is N2F2.

ii)

23 A piece of copper of mass 26.78 g was immersed in a colourless solution of nitrate of metal

X in a beaker. A silvery deposit of X formed on the copper surface and the solution

gradually turned pale blue. The beaker was allowed to stand. X was then washed with

distilled water and dried. The mass of X obtained was 1.94 g and the remaining copper had

a mass of 26.21 g.

a) Explain why the solution gradually turned pale blue.

b) Calculate the mass of copper reacted with the nitrate of X.

c) i) Explain why the solution was allowed to stand.

ii) Explain why the solid X should be washed and dried.

d) What is the number of moles of copper reacted?

e) What is the number of moles of X obtained?

f) What is the number of moles of X obtained when 1 mole of copper(II) ions is

formed?

g) Write an ionic equation for the above reaction.

(Relative atomic masses: Cu = 63.5, X = 107.9)

(10 marks)

Answer:

23 a) Copper reacted and blue copper(II) ions were formed. (1)

b) (26.78 − 26.21) g = 0.570 g (1)

c) i) To allow the solid formed to settle and deposit on the bottom of beaker. (1)

ii) Washing helps to remove any water soluble impurities. (1)

Drying allows the water in solid X to evaporate off, so more accurate result can be

obtained. (1)

d) 0.570 g ÷ 63.5 g mol-1 = 8.98 10-3 mol (1)

e) 1.94 g ÷ 107.9 g mol-1 = 0.0180 mol (1)

f) Mole ratio of X to Cu = 0.0180 : 8.98 10-3 = 2 : 1 (1)

Number of moles of X obtained = 2 mol (1)

g) Cu(s) + 2X+(aq) Cu2+(aq) + 2X(s) (1)

24 A student tried to extract lead from lead(II) oxide. He placed 10.0 g of lead(II) oxide and

10.0 g of carbon powder in a crucible and heated the mixture with a Bunsen flame.

a) Draw an experimental set-up for the extraction of lead(II) oxide.

b) i) Write a chemical equation for the reaction involved.

ii) Suggest ONE observation for the reaction.

c) i) Determine which reagent is in excess.

ii) Calculate the maximum mass of lead that could be obtained.

d) In fact, the student only obtained 7.10 g of lead.

i) Calculate the percentage yield of the reaction.

ii) Suggest ONE reason why the student cannot get the maximum mass of lead.

e) Another oxide of lead has a chemical formula of Pb3O4.

Pb3O4 is known to be a mixed oxide composed of PbO and PbO2. Deduce the mole

ratio of PbO to PbO2 in Pb3O4.

(Relative atomic masses: C = 12.0, O = 16.0, Pb = 207.2)

(12 marks)

Answer:

24 a)

(2)b) i) 2PbO(s) + C(s) 2Pb(s) + CO2(g) (1)

ii) Shiny pieces of solids would be observed. (1)

c) i) Number of moles of PbO = 10.0 g ÷ 223.2 g mol-1 = 0.0448 mol (1)

Number of moles of C = 10.0 g ÷ 12.0 g mol-1 = 0.833 mol (1)

According to the equation, 2 moles of PbO react with 1 mole of C.

Hence, 0.0448 mole of PbO would react with 0.0224 mole of C.

Therefore, carbon is in excess. (1)

ii) Maximum mass of Pb obtained = 0.0448 mol 207.2 g mol -1 = 9.28 g (1)

d) i) Percentage yield of reaction =

= 76.5% (1)

ii) The temperature is not high enough. / Not enough time allowed for the reaction to

take place. (1)

e) Let the mole ratio of PbO : PbO2 be x : y.

= =

x = 2, y = 1 (1)

\ Pb3O4 is a mixture of PbO and PbO2 in a mole ratio of 2 : 1. (1)

25 a) Hydrogen can reduce copper(II) oxide to copper. The experiment can be carried out

using the set-up shown below.

i) Write a chemical equation for the reaction between hydrogen and copper(II)

oxide.

ii) Suggest why it is necessary to burn the residual hydrogen in the set-up.

iii) What mass of copper would be obtained if 9.54 g of the oxide were consumed

in

the reaction?

b) Hydrogen is also used to manufacture ammonia by reacting with nitrogen according to

the following equation:

N2(g) + 3H2(g) 2NH3(g)

i) What does the sign ‘ ’ in the equation stand for?

ii) In the manufacturing process, a sufficient amount of hydrogen is allowed to

react

with 560 g of nitrogen. 102 g of ammonia are obtained. What is the percentage

conversion of nitrogen to ammonia?

(Relative atomic masses: H = 1.0, O = 16.0, N = 14.0, Cu = 63.5)

(8 marks)

Answer:

25 a) i) CuO(s) + H2(g) Cu(s) + H2O(l) (1)

ii) Hydrogen is explosive / flammable. (1)

iii) Number of moles of CuO consumed= Number of moles of Cu obtained

= 9.54 g ÷ (63.5 + 16.0) g mol-1

= 0.120 mol (1)

Mass of copper obtained = 0.120 mol 63.5 g mo l-1

= 7.62 g (1)

b) i) The reaction is reversible. (1)

ii) Number of moles of N2 reacted = 560 g ÷ (2 14.0 g) mol-1

= 20.0 mol (1)

Theoretical yield of NH3 = 17.0 g mol-1 2 20.0 mol

= 680 g (1)

Percentage conversion of N2 to NH3 = 100%

= 15.0% (1)

26 Compounds of manganese (Mn) have important uses in industry. Manganese nodules are

widely dispersed on the floor of some deep oceans. Manganese is present in the nodules

mainly as a form of manganese(IV) oxide MnO2. A nodule of mass 15.0 g was found to

contain 0.0400 mole of manganese(IV) oxide.

a) Calculate the percentage by mass of manganese(IV) oxide in the nodule.

b) Manganese has a hydrated sulphate with the formula MnSO4nH2O. On strong

heating,

20.1 g of the sulphate produced 7.51 g of water. What is the value of n?

(Relative atomic masses: H = 1.0, O = 16.0, S = 32.1, Mn = 54.9)

c) Pure manganese slowly reacts with cold water, in a way similar to calcium. In an

experiment, a few pieces of calcium granules are added to a beaker of cold water.

i) Give TWO observations when calcium reacts with cold water.

ii) Give a chemical equation for the reaction of calcium with water.

iii) Draw a labelled diagram of the set-up for conducting the experiment and

collecting the gas produced.

iv) Sodium also reacts with cold water. State TWO differences in observation

when

sodium and calcium are added separately to cold water.

(11 marks)

Answer:

26 a) Mass of MnO2 in the nodule = 0.0400 mol 86.9 g mol-1

= 3.48 g (1)

Percentage by mass of MnO2 in the nodule = 100%

= 23.2% (1)

b) (1)

n = 5 (1)

c) i) Any TWO of the following: (1 2)

Gas bubbles are given off.

Calcium dissolves.

A milky suspension is formed.

Calcium sinks in water.

ii) Ca(s) + 2H2O(l) Ca(OH)2(s) + H2(g) (1)

iii)

(2)

iv) Sodium floats on the surface of water while calcium sinks. (1)

Sodium moves rapidly on the surface of water and may burn with a golden yellow

flame. Calcium stays at the bottom of the beaker and does not move. (1)

27 Tin (Sn) displaces copper from copper(II) sulphate solution. Cadmium (Cd) displaces tin

from tin(II) chloride solution. The three metals and their cations are as follows:

Sn / Sn2+, Cu / Cu2+, Cd / Cd2+.

a) Write ionic equations for the two displacement reactions described above.

b) Use the information given, deduce the reactivity order of the metals, starting with the

most reactive one.

c) State whether you would expect each of the following reactions to occur.

Explain your answers.

i) Sn(s) + Cd2+(aq) Sn2+(aq) + Cd(s)

ii) Cd(s) + Cu2+(aq) Cd2+(aq) + Cu(s)

d) Explain why copper(II) sulphate solution CANNOT be stored in tin containers.

e) Aluminium can also displace copper from copper(II) sulphate solution.

i) Write a chemical equation for the reaction involved.

ii) What is the percentage yield of copper in a reaction which produces

2.58 g of copper from 1.61 g of aluminium and excess copper(II) sulphate solution.

(Relative atomic masses: Al = 27.0, Cu = 63.5)

(10 marks)

Answer:

27 a) Sn(s) + Cu2+(aq) Sn2+(aq) + Cu(s) (1)

Cd(s) + Sn2+(aq) Cd2+(aq) + Sn(s) (1)

b) Cd > Sn > Cu (1)

c) i) No reaction. As tin is less reactive than cadmium, it cannot displace

cadmium from the solution of a cadmium compound. (1)

ii) It will occur. As cadmium is more reactive than copper, it can displace

copper from the solution of a copper compound. (1)

d) Tin will react with copper(II) sulphate solution and will eventually wear away. (1)

e) i) 2Al(s) + 3CuSO4(aq) Al2(SO4)3(aq) + 3Cu(s) (1)

ii) Number of moles of Al reacted = 1.61 g ÷ 27.0 g mol-1

= 0.0596 mol (1)

Theoretical yield of Cu = 0.0596 mol 63.5 g mol-1

= 5.68 g (1)

Percentage yield of Cu = 100%

= 45.4% (1)

28 a) Calcite is a very pure form of calcium carbonate which reacts with dilute hydrochloric

acid according to the following equation:

CaCO3(x) + 2HCl(aq) CaCl2(y) + H2O(z) + CO2(g)

2.60 g of calcite were added to 0.0150 mole of hydrochloric acid in a beaker.

Calcite was in excess.

i) Give the state symbols represented by x, y and z in the equation.

ii) Calculate the mass of calcite left unreacted.

iii) Describe what could be done to check the result obtained in (b).

b) An experiment was carried out to determine the percentage by mass of

calcium carbonate in a sample of mass 3.10 g. The set-up shown below was used:

The graph shows the results obtained in the experiment.

i) Find, from the graph, the mass of gas liberated from the reaction of the sample with

hydrochloric acid.

ii) Calculate the percentage by mass of calcium carbonate in the sample.

iii) Suggest ONE source of error in the experiment.

(Relative atomic masses: C = 12.0, O = 16.0, Ca = 40.1)

(10 marks)

Answer:

28 a) i) x : s, y : aq, z : l. (1)

ii) Number of moles of calcite added = 2.60 g ÷ 100.1 g mol-1

= 0.0260 mol (1)

According to the equation, 1 mole of CaCO3 reacts with 2 moles of HCl.

0.0150 mole of HCl reacts with 0.00750 mole of CaCO3.

Number of moles of calcite left = (0.0260 − 0.00750) mol

= 0.0185 mol (1)

Mass of calcite left = 0.0185 mol 100.1 g mol-1

= 1.85 g (1)

iii) Separate calcite from the reaction mixture, dry and weigh it. (1)

b) i) 1.10 g (187.6 g −186.5 g) (1)

ii) Number of moles of CO2 liberated = 1.10 g ÷ 44.0 g mol-1

= 0.0250 mol (1)

According to the equation, 1 mole of CaCO3 produces 1 mole of CO2.

Thus 0.0250 mole of CaCO3 produces 0.0250 mole of CO2 in the reaction.

Number of moles of CaCO3 in the sample = 0.0250 mol

Mass of CaCO3 in the sample = 0.0250 mol 100.1 g mol-1

= 2.50 g (1)

Percentage by mass of CaCO3 in the sample = 100%

= 80.6% (1)

iii) Some carbon dioxide dissolve in the acid. (1)

29 Potassium is obtained from the mineral carnallite (KClMgCl26H2O). An experiment was

carried out to determine the percentage by mass of carnallite in an impure sample. The mass

of the impure sample was 6.17 g. It was dissolved in water. An excess of acidified silver

nitrate solution was added. The silver chloride precipitate was filtered, washed and dried.

It had a mass of 8.61 g.

a) i) Silver ion and chloride ion react to give silver chloride according to the

following

equation:

Ag+(x) + Cl-(y) AgCl(z)

Give the state symbols represented by x, y and z in the equation.

ii) Explain why an excess of silver nitrate solution was used in the experiment.

iii) Calculate the number of moles of silver chloride obtained in the experiment.

iv) Calculate the percentage by mass of carnallite in the impure sample.

(Relative atomic masses: H = 1.0, O = 16.0, Mg = 24.3, Cl = 35.5, K = 39.1, Ag

= 107.9)

b) Suggest how potassium is extracted from carnallite.

c) In another experiment, potassium is heated in the air.

i) Describe the observable changes of the experiment.

ii) Write a chemical equation for the reaction involved.

iii) Suggest how potassium should be stored in the laboratory.

(11 marks)

Answer:

29 a) i) x : aq, y : aq, z : s. (1)

ii) To react with all the chloride ions. (1)

iii) Number of moles of AgCl = 8.61 g ÷ 143.4 g mol-1

= 0.0600 mol (1)

iv) 1 mole of KClMgCl26H2O contains 3 moles of chloride ions.

1 mole of KClMgCl26H2O gives 3 moles of AgCl when reacted with excess

AgNO3(aq).

Number of moles of KClMgCl26H2O in the sample = mol

= 0.0200 mol (1)

Mass of KClMgCl26H2O in the sample

= 0.0200 mol [39.1 + 24.3 + 3 35.5 + 6 (2 1.0 + 16.0)] g mol-1

= 5.56 g

(1)

Percentage by mass of KClMgCl26H2O in the sample

= 100%

= 90.1% (1)

b) Electrolysis of molten carnallite (1)

c) i) Potassium burns vigorously with a purple flame. (1)

A white smoke forms. (1)

ii) 4K(s) + O2(g) 2K2O(s) (1)

iii) Store it in paraffin oil. (1)

30 Explain each of the following:

a) Aluminium does NOT react with steam unless when the aluminium is washed with

mercury(II) chloride solution.

b) Silver nitrate solution CANNOT be kept in an iron bucket.

c) Aluminium, rather than copper, is used in making overhead power cables.

d) When calcium reacts with dilute sulphuric acid, gas bubbles are given off for a short

while and then stop.

e) Zinc can be extracted from its molten ore by electrolysis. Yet in practice, it is usually

extracted by heating its oxide with coke.

f) It is NOT advisable to buy a can of food if there are scratches on the iron body of the

can.

g) Galvanized iron is NOT used in making food cans.

(12 marks)

Answer:

30 a) A layer of aluminium oxide is attached to the surface of aluminium and this prevents

the reaction of aluminium. (1)

Mercury(II) chloride solution can remove this oxide layer and allow the aluminium

underneath to react. (1)

b) There is a displacement reaction between silver nitrate solution and iron. (1)

It will cause the iron to dissolve. (1)

c) Aluminium is lighter and stronger than copper. (1, 1)

d) Insoluble calcium sulphate forms in the reaction. (1)

It covers the calcium metal and prevents further reaction. (1)

e) Electrolysis is an expensive extraction method. (1)

f) When the tin coating of a food can is damaged, the iron rusts more quickly than when

it is alone (1)

because tin is less reactive than iron. (1)

g) Zinc ions are toxic. (1)

31 a)

The above figure shows the location of a factory which extracts zinc from its ore, zinc

blende (ZnS). The flow diagram below shows how zinc is extracted in the factory.

In Stage I, the ore is heated strongly in air. A yellow compound X is formed which

becomes white when cold. Besides, an acidic gas Y is evolved and this is emitted to the

surroundings from chimneys.

i) (1) Write a chemical equation for the reaction occurred in Stage I.

(2) Give the names of compound X and gas Y.

ii) In Stage II, X is heated strongly with a black powder.

(1) Identify the black powder.

(2) Write a chemical equation for the reaction occurred in Stage II.

iii) State ONE use of zinc.

b) Statues A and B are mainly made of iron. It is found that statue A rusts more quickly

than B.

i) Give a reason for this.

ii) Suggest ONE method to slow down the corrosion of the statues.

c) Zinc reacts with dilute hydrochloric acid to give hydrogen.

i) Write a chemical equation for the reaction involved.

ii) A sample of hydrochloric acid containing 2.92 g of HCl is added to 3.27 g of

zinc. Calculate the mass of hydrogen produced.

(Relative atomic masses: H = 1.0, Cl = 35.5, Zn = 65.4)

(14 marks)

Answer:

31 a) i) (1) 2ZnS(s) + 3O2(g) 2ZnO(s) + 2SO2(g) (1)

(2) X: Zinc oxide (1)

Y: Sulphur dioxide (1)

ii) (1) Carbon (1)

(2) 2ZnO(s) + C(s) 2Zn(s) + CO2(g) (1)

iii) Making galvanized iron / casings of dry cells (1)

b) i) Wind brings acidic sulphur dioxide gas to statue A but not B. (1)

Acidic gas speeds up the corrosion of iron. (1)

ii) Metal-plating of the statues (1)

c) i) Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g) (1)

ii) Number of moles of HCl used = 2.92 g ÷ 36.5 g mol-1

= 0.0800 mol (1)

Number of moles of Zn used = 3.27 g ÷ 65.4 g mol-1

= 0.0500 mol (1)

According to the equation, 1 mole of Zn reacts with 2 moles of HCl.

Hence, 0.0800 mole of HCl reacts with 0.0400 mole of Zn. Therefore, Zn is in

excess. (1)

Mass of hydrogen produced = 0.0800 mol ÷ 2 2.0 g mol-1

= 0.0800 g

(1)

32 Explain briefly how the protection against rusting can be achieved in each of the following

cases.

a) Underground iron gas pipes are joined to magnesium.

b) Cloth hangers are coated with plastic.

c) Bus stop signs are painted.

d) Bicycle chains are greased.

e) A car body is connected to the negative terminal of a car battery.

(10 marks)

Answer:

32 a) This is sacrificial protection. Magnesium corrodes instead of iron (1)

because magnesium is higher than iron in the reactivity series. (1)

b) Plastic acts as a protective layer (1)

to prevent air and moisture from reaching the iron and hence prevent rusting. (1)

c) Paint gives a protective layer to iron (1)

so that iron can be kept away from direct contact with air and moisture, hence rusting

can be prevented. (1)

d) Grease protects the moving iron parts (1)

by preventing air and water to come into contact with the iron, hence rusting can be

prevented. (1)

e) The negative terminal of the battery supplies electrons to the car body (1)

which prevent it from being oxidized. (1)

33 Three test tubes are set up in the diagram shown below:

The tubes are left for three days.

a) In which tube(s) will rusting occur?

b) What is the function of the anhydrous calcium chloride used in test tube A?

c) What is the function of the oil used in test tube B?

d) Suggest TWO conditions needed for rusting.

e) Draw a labelled diagram of a set-up that can be used to show that the presence of

ionic

substances can increase the rate of rusting. State also the expected observation.

(7 marks)

Answer:

33 a) Tube C (1)

b) To absorb the moisture in the air in the tube. (1)

c) To prevent the oxygen in the air from dissolving into the boiled water. (1)

d) Water and oxygen (1, 1)

e)

(1)

Compare the degree of rusting of the nail with that in tube C after a certain period of

time. The nail in this tube forms more rust. (1)

34 The rusting of iron is investigated by giving five identical iron nails different treatments.

One nail is left untreated. All six nails are then exposed to air for one week. The results are

given in the table below.

Nail Treatment Mass of nail and coating

before exposed to air

Mass of nail and coating

after exposed to air

A Painting 7.0 g 7.3 g

B Coating with wax 7.0 g 6.5 g

C Nickel-plating 7.0 g 7.0 g

D Galvanizing 7.0 g 7.1 g

E Dipping into salt solution 6.9 g 8.9 g

F Untreated 6.9 g 8.2 g

a) Explain why the mass of the untreated nail has increased after exposed to air.

b) Which nail is best protected from rusting? Explain your answer.

c) Which treatment make the nail rust faster? Explain your answer.

d) Explain in which case was a mistake made in the weighing of the nail.

e) What is meant by the treatment ‘galvanizing’?

f) Bridges are protected from rusting by attaching blocks of magnesium to them.

i) What is the term used to describe this kind of protection against rusting?

ii) Suggest why this method is NOT used to protect iron nails from rusting.

g) Explain why rusting is a destructive process but corrosion of aluminium is a useful

process.

(14 marks)

Answer:

34 a) Because iron reacts with oxygen and water in air to form rust (hydrated iron (III)

oxide). (1)

Formation of hydrated iron (III) oxide has increased the mass of the nail. (1)

b) The nail coated with nickel. (1)

Because the mass of the nickel-plated nail has not increased after exposed to air. (1)

c) Dipping into salt solution. (1)

The presence of ionic substances speeds up rusting. (1)

d) Nail B, since the mass of the nail should be the same or higher after the experiment. (1)

e) Coating the iron with zinc. (1)

f) i) Sacrificial protection (1)

ii) It is expensive. (1)

g) When the rusting of iron occurs, the rust tends to fall off as it is formed. A fresh iron

surface is exposed and so rusting goes on. This causes disintegration of the metal. (2)

When aluminium reacts with oxygen in the air, an even coating of aluminium oxide

forms. This oxide layer sticks to the metal surface and is not permeable to oxygen and

water. It protects the metal beneath from further attack. (2)

35 Aluminium and iron are the two most abundant metals in the Earth’s crust.

a) Explain why iron was discovered about four thousand years ago while aluminium was

discovered less than two hundred years ago.

b) Both aluminium and iron can be used to make window frames.

i) Suggest how each metal is treated to prevent corrosion in this usage.

ii) Explain why most window frames are now made of aluminium instead of iron.

c) The diagram below shows a can of fruit juice. The body of the can is made of iron

coated with tin. The top of the can and the ring-pull are made of aluminium.

i) Suggest ONE reason why the iron body is coated with tin.

ii) Suggest ONE reason why aluminium, rather than iron, is used for making the

ring-pull.

iii) There is a trend for manufacturers to use cans made entirely of aluminium for

fruit juice storage. Suggest ONE advantage and ONE disadvantage of this action.

(10 marks)

Answer:

35 a) Aluminium is more reactive than iron. (1)

The extraction of iron is easier than that of aluminium. Therefore, iron was discovered

much earlier than aluminium. (1)

b) i) The aluminium undergoes anodization to increase the thickness of the oxide layer.

This makes the aluminium much more resistant to corrosion. (1)

The iron is painted so as to prevent oxygen and water from reaching it.

The paint layer protects the iron beneath from rusting. (1)

ii) As soon as the paint on the iron is scratched, rusting starts. (1)

Aluminium reacts with oxygen in the air to give an even coating of oxide on the

surface. The oxide layer is not permeable to oxygen and water. It protects the

metal beneath from further attack. (1)

c) i) To protect iron from rusting. (1)

ii) Aluminium is softer than iron so that the ring-pull can be pulled off more easily.(1)

iii) Advantage (Any one of the following): (1)

Aluminium is lighter than iron.

Aluminium can be recycled more easily.

Aluminium is more corrosion resistant than iron.

Aluminium can be dyed more easily.

Disadvantage (Any one of the following): (1)

Aluminium is more expensive than iron.

Aluminium is not as strong as iron.

36 Aluminium is the most abundant metal in the Earth’s crust.

a) i) Name an aluminium ore.

ii) Suggest how aluminium can be extracted from its ore.

b) One of the special properties of aluminium is that it has high corrosion resistance.

i) Explain why aluminium has such a high corrosion resistance.

ii) The corrosion resistance of aluminium can be further improved by a method.

(1) Name this method.

(2) Draw a labelled diagram of the laboratory set-up used for this method.

c) The reaction of aluminium and zinc nitrate solution can be represented by the

following equation:

2Al(s) + 3Zn(NO3)2(aq) 2Al(NO3)3(aq) + 3Zn(s)

i) Give TWO observations of the above reaction.

ii) Explain why the above reaction is a displacement reaction.

iii) If 9.00 g of aluminium are added to excess zinc nitrate solution, calculate the

maximum amount of zinc that can be obtained.

(Relative atomic masses: Al = 27.0, Zn = 65.4)

(12 marks)

Answer:

36 a) i) Bauxite (1)

ii) Electrolysis of molten aluminium oxide (1)

b) i) There is a layer of aluminium oxide attached to the metal surface. (1)

ii) (1) Aluminium anodization (1)

(2)

(2)c) i) Aluminium dissolves. (1)

A grey metal deposits. (1)

ii) The more reactive aluminium displaces the less reactive zinc from zinc nitrate

solution. (1)

iii) Number of moles of aluminium added = 9.00 g ÷ 27.0 g mol-1

= 0.333 mol (1)

Number of moles of zinc formed = 0.333 mol

= 0.500 mol (1)

Maximum mass of zinc obtained = 0.500 mol 65.4 g mo l-1

= 32.7 g (1)

37 You are provided with the following materials and apparatus:

Bunsen burner, test tube holder, wooden splints, test tubes, delivery tube and limewater

Suggest how you would carry out three chemical tests, using the materials and apparatus

listed above, to distinguish between silver oxide, iron(III) oxide and carbon powder.

Your answer should include the expected observation of each test.

(You are required to give a paragraph-length answer. For this question, 6 marks will be

awarded for chemical knowledge and 3 marks for effective communication.)

(You are NOT required to write chemical equations. Answers in the form of flow diagrams

will NOT be marked.)

(9 marks)

Answer:

37 Heat the three substances alone in air, (1)

silver oxide will decompose into silvery solids and a gas which can relight a glowing splint

is released. (1)

Carbon powder will burn to red-hot and a gas is released. Pass the gas into limewater with a

delivery tube. (1)

It can turn limewater milky. (1)

Heat iron (III) oxide with carbon powder, (1)

the black solid will turn into a silvery-grey solid and a gas is released. The gas can turn

limewater milky. (1)

(3 marks for effective communication)

38 You are provided with the following materials and apparatus:

3 clean iron nails, magnesium ribbon, copper foil, gel solution, rust indicator and 3 petri

dishes

Suggest an experiment, with the expected observation and explanations, which allows you

to determine the reactivity order of magnesium, iron and copper.



(Answers in the form of flow diagrams will NOT be marked.)

(9 marks)

Answer:

38 Wrap two iron nails with magnesium ribbon and copper foil separately. (1)

Place an iron nail and the two wrapped iron nails into three petri dishes separately. Pour gel

solution mixed with rust indicator to each petri dish until each iron nail is completely

covered. (1)

Leave the dishes for about one to two days. (1)

The indicator shows a blue colour when rusting occurs. The reactivity can be determined by

observing the presence of blue colour near the iron nails. (1)

The more reactive metal (Mg) can protect the iron nail from rusting. Therefore, no blue

colour will be observed near the iron nail wrapped with magnesium. (1)

The less reactive metal (Cu) will speed up the rusting process. Therefore, a blue colour will

be observed quickly near the iron nail wrapped with copper. (1)

The reactivity order is thus Cu < Fe < Mg.


39 Protective coatings are commonly used for preventing rusting. Discuss the underlying

principle involved in TWO kinds of protective coating and their limitations, with reference

to specific examples.



(9 marks)

Answer:

39 Oxygen and water must be present for rusting to occur. (1)

Protective coatings on iron articles prevent both oxygen and water from reaching the iron

beneath and thus protecting the iron from rusting. (1)


Example 1:

Painting is applied on articles unlikely to be scratched. Cars, bridges and iron railings are

protected from rusting by painting.

However, as soon as the paint is scratched, the metal is exposed to air and rusting starts.

Therefore, painting is not suitable for iron moving parts of machines.

Example 2:

For moving parts of machine, such as door hinges and motors, oil or grease is applied for

preventing rusting. Oil or grease has a lubricating purpose also.

However, oil or grease must be reapplied constantly. Therefore, this method is unsuitable

for large structures.

Example 3:

Coat hangers and dish racks are often protected with a thin coating of plastic.

This protection lasts longer and improves the appearance of the articles.

However, coating iron articles with plastic is more expensive than painting.

Example 4:

Iron can be coated with a thin layer of tin for preventing rusting. Food cans are usually

made of mild steel coated with a thin layer of tin because tin ions are non-poisonous.

However, once the tin coating is damaged, the iron rusts more quickly than when it is alone.

This is because iron is more reactive than tin.

Example 5:

Iron can be coated with a layer of zinc for preventing rusting. When the zinc coating is

damaged, zinc still protects the iron from rusting. This is because zinc is more reactive than

iron and corrodes instead of iron. The protection lasts as long as the zinc lasts.

However, iron coated with zinc is not suitable for making food cans because zinc ions are

poisonous.

Example 6:

A very thin layer of metal can be applied on iron by electroplating. Chromium- and nickel-

platings protect iron from both oxygen and water. These platings are not easily

scratched off. Chromium-plated articles look more attractive.

However, the cost of chromium-plating is quite high.


QB_metal_ans

Documents

Transcript of QB_metal_ans