GCSE Chemistry Practice Paper 3

Do not write outside this box

Instructions to Students

Use black ink or black ball-point pen.
Fill in the boxes at the top of this page with your details if required.
Answer all questions in the spaces provided.
Do all rough work in this book. Cross through any work you do not want to be marked.
In all calculations, show clearly how you work out your answer.
A Periodic Table is provided as a separate insert if required.
Calculators may be used.

Information for Candidates

This practice paper is designed to support student revision for the GCSE Chemistry examinations. It contains questions covering atomic structure, periodic table trends, structure and bonding, quantitative chemistry, chemical changes, electrolysis, and energy changes. The marks for individual questions and parts of questions are shown in round brackets.

Do not write outside this box

This resource is an independent educational tool created to support student revision. It is completely independent and is not endorsed by, affiliated with, or sponsored by any official examination board. All trademarked terms are used under Nominative Fair Use purely for descriptive compatibility indexing. Licensed for individual personal use only.
Chemistry Made Easy is an independent resource. Not affiliated with or endorsed by AQA, Pearson Edexcel, or the IBO.

Do not write outside this box

Question 1 [16 Marks]

Early chemists attempted to classify elements by arranging them based on their properties.

(6)

(a) Compare Mendeleev's periodic table with John Newlands' octaves. Explain how Mendeleev overcame the problems of early periodic tables, and why his periodic table was eventually accepted by the scientific community.

(4)

(b) Chlorine exists in nature as two isotopes: chlorine-35 and chlorine-37. The relative abundance of chlorine-35 is 75.77% and the relative abundance of chlorine-37 is 24.23%.
Calculate the relative atomic mass (Ar) of chlorine. Give your answer to 2 decimal places. Show your working clearly.

Do not write outside this box

This resource is an independent educational tool created to support student revision. It is completely independent and is not endorsed by, affiliated with, or sponsored by any official examination board. All trademarked terms are used under Nominative Fair Use purely for descriptive compatibility indexing. Licensed for individual personal use only.
Chemistry Made Easy is an independent resource. Not affiliated with or endorsed by AQA, Pearson Edexcel, or the IBO.

Do not write outside this box

(4)

(c) Oxygen has an atomic number of 8, and sulfur has an atomic number of 16. Write the electronic configuration of both oxygen and sulfur. Explain why both elements are placed in Group 6 of the modern periodic table.

(2)

(d) State how the modern periodic table is ordered, and explain how this arrangement differs from early periodic tables before the discovery of subatomic particles.

Question 2 [22 Marks]

Carbon dioxide is a simple molecular compound formed by covalent bonding.

(4)

(a) Draw a dot-and-cross diagram to show the covalent bonding in a molecule of carbon dioxide (CO2). You should show only the outer-shell electrons.

Do not write outside this box

This resource is an independent educational tool created to support student revision. It is completely independent and is not endorsed by, affiliated with, or sponsored by any official examination board. All trademarked terms are used under Nominative Fair Use purely for descriptive compatibility indexing. Licensed for individual personal use only.
Chemistry Made Easy is an independent resource. Not affiliated with or endorsed by AQA, Pearson Edexcel, or the IBO.

Do not write outside this box

(6)

(b) Graphite and graphene are allotropes of carbon with different structures. Compare the structures of graphite and graphene. Describe how their bonding explains why graphite is used as a lubricant and how graphene is strong and conducts electricity.

(6)

(c) Carbon dioxide (CO2) has a low boiling point of -78 degrees Celsius and does not conduct electricity. Explain these physical properties in terms of structure and bonding.

Do not write outside this box

This resource is an independent educational tool created to support student revision. It is completely independent and is not endorsed by, affiliated with, or sponsored by any official examination board. All trademarked terms are used under Nominative Fair Use purely for descriptive compatibility indexing. Licensed for individual personal use only.
Chemistry Made Easy is an independent resource. Not affiliated with or endorsed by AQA, Pearson Edexcel, or the IBO.

Do not write outside this box

(6)

(d) Silicon dioxide (SiO2) has a giant covalent structure. Compare the structure, bonding, and physical properties of carbon dioxide and silicon dioxide. Explain why their melting points are so different.

Do not write outside this box

This resource is an independent educational tool created to support student revision. It is completely independent and is not endorsed by, affiliated with, or sponsored by any official examination board. All trademarked terms are used under Nominative Fair Use purely for descriptive compatibility indexing. Licensed for individual personal use only.
Chemistry Made Easy is an independent resource. Not affiliated with or endorsed by AQA, Pearson Edexcel, or the IBO.

Do not write outside this box

Question 3 [25 Marks]

Chemical calculations allow chemists to predict masses and concentrations of reactants and products.

(8)

(a) Ammonia (NH3) is synthesised by reacting nitrogen gas with hydrogen gas as shown:

N2(g) + 3H2(g) → 2NH3(g)

A student reacts 56.0 g of nitrogen (N2) with 15.0 g of hydrogen (H2).
Show by calculation which reactant is the limiting reactant, and calculate the maximum theoretical mass of ammonia produced in grams.
Relative atomic masses (Ar): H = 1; N = 14

(9)

(b) A student carries out a titration to determine the concentration of a potassium hydroxide (KOH) solution.
The student titrates 25.0 cm3 of the potassium hydroxide solution against 18.5 cm3 of a standard sulfuric acid (H2SO4) solution of concentration 0.125 mol/dm3.
The equation for the reaction is:

H2SO4(aq) + 2KOH(aq) → K2SO4(aq) + 2H2O(l)

Calculate the concentration of the potassium hydroxide solution in mol/dm3 and in g/dm3. Give your answer to 3 significant figures.
Relative atomic masses (Ar): H = 1; O = 16; K = 39

Do not write outside this box

This resource is an independent educational tool created to support student revision. It is completely independent and is not endorsed by, affiliated with, or sponsored by any official examination board. All trademarked terms are used under Nominative Fair Use purely for descriptive compatibility indexing. Licensed for individual personal use only.
Chemistry Made Easy is an independent resource. Not affiliated with or endorsed by AQA, Pearson Edexcel, or the IBO.

Do not write outside this box

(3)

(c) In the synthesis of ammonia reaction in part (a), the theoretical yield was calculated. In an actual laboratory experiment, the student obtained 51.0 g of ammonia.
Calculate the percentage yield of ammonia. Give your answer to 3 significant figures.

(2)

(d) Calculate the volume, in dm3, occupied by 2.00 moles of nitrogen gas at room temperature and pressure (RTP). Assume 1 mole of any gas occupies 24.0 dm3 at RTP.

(3)

(e) Industrial chemical processes rarely achieve a 100% percentage yield. State three reasons why the actual yield of a chemical reaction is usually less than the theoretical maximum yield.

Do not write outside this box

This resource is an independent educational tool created to support student revision. It is completely independent and is not endorsed by, affiliated with, or sponsored by any official examination board. All trademarked terms are used under Nominative Fair Use purely for descriptive compatibility indexing. Licensed for individual personal use only.
Chemistry Made Easy is an independent resource. Not affiliated with or endorsed by AQA, Pearson Edexcel, or the IBO.

Do not write outside this box

Question 4 [23 Marks]

Electrolysis uses electrical energy to decompose liquid electrolytes.

(8)

(a) A student sets up an electrolysis cell containing dilute sulfuric acid (H2SO4) using inert platinum electrodes, as shown in the diagram below.
Explain the chemical reactions taking place at each electrode. Identify the products formed, explain which ions migrate to each electrode, and write the balanced half-equations for the reactions at the anode and the cathode.

Do not write outside this box

This resource is an independent educational tool created to support student revision. It is completely independent and is not endorsed by, affiliated with, or sponsored by any official examination board. All trademarked terms are used under Nominative Fair Use purely for descriptive compatibility indexing. Licensed for individual personal use only.
Chemistry Made Easy is an independent resource. Not affiliated with or endorsed by AQA, Pearson Edexcel, or the IBO.

Do not write outside this box

(6)

(b) Required Practical 3: A student investigates the electrolysis of brine (aqueous sodium chloride, NaCl) using carbon electrodes.
Describe the product formed at the anode and the product formed at the cathode. Explain why these specific products form instead of sodium metal and oxygen gas, and state which useful substance is left in the solution.

(6)

(c) Acid strength refers to the degree of ionisation of acid molecules in solution. A student has a solution of hydrochloric acid of pH 2.00, and a solution of a weak acid of pH 5.00.
Show by calculation the difference in hydrogen ion concentration [H+] between these two solutions. Explain what is meant by a strong acid and a weak acid, referring to how they ionise in water.

Do not write outside this box

This resource is an independent educational tool created to support student revision. It is completely independent and is not endorsed by, affiliated with, or sponsored by any official examination board. All trademarked terms are used under Nominative Fair Use purely for descriptive compatibility indexing. Licensed for individual personal use only.
Chemistry Made Easy is an independent resource. Not affiliated with or endorsed by AQA, Pearson Edexcel, or the IBO.

Do not write outside this box

(3)

(d) Required Practical 1: A student prepares a pure sample of copper(II) chloride crystals by reacting copper(II) oxide with dilute hydrochloric acid.
Write the balanced chemical equation for this reaction. Describe the filtration and crystallisation steps required to obtain dry, pure copper(II) chloride crystals from the reaction mixture.

Do not write outside this box

This resource is an independent educational tool created to support student revision. It is completely independent and is not endorsed by, affiliated with, or sponsored by any official examination board. All trademarked terms are used under Nominative Fair Use purely for descriptive compatibility indexing. Licensed for individual personal use only.
Chemistry Made Easy is an independent resource. Not affiliated with or endorsed by AQA, Pearson Edexcel, or the IBO.

Do not write outside this box

Question 5 [14 Marks]

The reaction between magnesium ribbon and hydrochloric acid is highly exothermic.

Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)

(6)

(a) Complete the energy profile diagram below for this reaction. Label the reactants and products, and show arrows for the activation energy (Ea) and the overall energy change (ΔH). Explain why this reaction is exothermic by referring to the diagram.

Do not write outside this box

This resource is an independent educational tool created to support student revision. It is completely independent and is not endorsed by, affiliated with, or sponsored by any official examination board. All trademarked terms are used under Nominative Fair Use purely for descriptive compatibility indexing. Licensed for individual personal use only.
Chemistry Made Easy is an independent resource. Not affiliated with or endorsed by AQA, Pearson Edexcel, or the IBO.

Do not write outside this box

(8)

(b) Hydrogen gas reacts with chlorine gas to produce hydrogen chloride gas:

H2(g) + Cl2(g) → 2HCl(g)

The table below shows the relevant bond energies:

Bond	Bond Energy / kJ/mol
H-H	436
Cl-Cl	242
H-Cl	431

Calculate the overall energy change for the reaction in kJ/mol. Explain whether this reaction is endothermic or exothermic, referring to the energy required to break bonds and the energy released when new bonds are formed.

Do not write outside this box

This resource is an independent educational tool created to support student revision. It is completely independent and is not endorsed by, affiliated with, or sponsored by any official examination board. All trademarked terms are used under Nominative Fair Use purely for descriptive compatibility indexing. Licensed for individual personal use only.
Chemistry Made Easy is an independent resource. Not affiliated with or endorsed by AQA, Pearson Edexcel, or the IBO.

Do not write outside this box

Group 1

Group 2

Transition Metals

Group 3

Group 4

Group 5

Group 6

Group 7

Group 0

KEY

relative atomic mass

H

atomic symbol

name

atomic (proton) number

* Lanthanides

** Actinides

1 H Hydrogen 1

4 He Helium 2

7 Li Lithium 3

9 Be Beryllium 4

11 B Boron 5

12 C Carbon 6

14 N Nitrogen 7

16 O Oxygen 8

19 F Fluorine 9

20 Ne Neon 10

23 Na Sodium 11

24 Mg Magnesium 12

27 Al Aluminium 13

28 Si Silicon 14

31 P Phosphorus 15

32 S Sulfur 16

35.5 Cl Chlorine 17

40 Ar Argon 18

39 K Potassium 19

40 Ca Calcium 20

45 Sc Scandium 21

48 Ti Titanium 22

51 V Vanadium 23

52 Cr Chromium 24

55 Mn Manganese 25

56 Fe Iron 26

59 Co Cobalt 27

59 Ni Nickel 28

63.5 Cu Copper 29

65 Zn Zinc 30

70 Ga Gallium 31

73 Ge Germanium 32

75 As Arsenic 33

79 Se Selenium 34

80 Br Bromine 35

84 Kr Krypton 36

85.5 Rb Rubidium 37

88 Sr Strontium 38

89 Y Yttrium 39

91 Zr Zirconium 40

93 Nb Niobium 41

96 Mo Molybdenum 42

98 Tc Technetium 43

101 Ru Ruthenium 44

103 Rh Rhodium 45

106 Pd Palladium 46

108 Ag Silver 47

112 Cd Cadmium 48

115 In Indium 49

119 Sn Tin 50

122 Sb Antimony 51

128 Te Tellurium 52

127 I Iodine 53

131 Xe Xenon 54

133 Cs Cesium 55

137 Ba Barium 56

139 La* Lanthanum 57

178.5 Hf Hafnium 72

181 Ta Tantalum 73

184 W Tungsten 74

186 Re Rhenium 75

190 Os Osmium 76

192 Ir Iridium 77

195 Pt Platinum 78

197 Au Gold 79

201 Hg Mercury 80

204 Tl Thallium 81

207 Pb Lead 82

209 Bi Bismuth 83

209 Po Polonium 84

210 At Astatine 85

222 Rn Radon 86

223 Fr Francium 87

226 Ra Radium 88

227 Ac** Actinium 89

267 Rf Rutherfordium 104

268 Db Dubnium 105

269 Sg Seaborgium 106

270 Bh Bohrium 107

269 Hs Hassium 108

278 Mt Meitnerium 109

281 Ds Darmstadtium 110

282 Rg Roentgenium 111

285 Cn Copernicium 112

286 Nh Nihonium 113

289 Fl Flerovium 114

289 Mc Moscovium 115

293 Lv Livermorium 116

294 Ts Tennessine 117

294 Og Oganesson 118

140 Ce Cerium 58

141 Pr Praseodymium 59

144 Nd Neodymium 60

145 Pm Promethium 61

150 Sm Samarium 62

152 Eu Europium 63

157 Gd Gadolinium 64

159 Tb Terbium 65

162.5 Dy Dysprosium 66

165 Ho Holmium 67

167 Er Erbium 68

169 Tm Thulium 69

173 Yb Ytterbium 70

175 Lu Lutetium 71

232 Th Thorium 90

231 Pa Protactinium 91

238 U Uranium 92

237 Np Neptunium 93

244 Pu Plutonium 94

243 Am Americium 95

247 Cm Curium 96

247 Bk Berkelium 97

251 Cf Californium 98

252 Es Einsteinium 99

257 Fm Fermium 100

258 Md Mendelevium 101

259 No Nobelium 102

266 Lr Lawrencium 103

Do not write outside this box

This resource is an independent educational tool created to support student revision. It is completely independent and is not endorsed by, affiliated with, or sponsored by any official examination board. All trademarked terms are used under Nominative Fair Use purely for descriptive compatibility indexing. Licensed for individual personal use only.
Chemistry Made Easy is an independent resource. Not affiliated with or endorsed by AQA, Pearson Edexcel, or the IBO.