2 The fractional distillation of petroleum is shown in Fig. 2.1. hot petroleum A … fraction B gasoline D … C naphtha E … Fig. 2.1 (a) A, B, C, D and E are five fractions. The names of these five fractions are bitumen, diesel oil, gasoline, naphtha and refinery gas. (i) Identify these fractions by completing Fig. 2.1. Two have been done for you. [1] (ii) Fraction A is a mixture of compounds. They are all hydrocarbons. Describe two other ways in which the compounds in fraction A are similar. 1. … 2. … [2] (iii) State one use for naphtha. … [1] (b) Methane, CH4, and pentane, C5H12, are members of the homologous series of alkanes. (i) State what is meant by a homologous series. … … … … [2] (ii) Write the balanced symbol equation for the complete combustion of pentane, C5H12, in oxygen. … [2] [Total: 8]

2(a)(i) A refinery gas B (gasoline) C (naphtha) D diesel oil E bitumen ; all three correct for one mark 1 2(a)(ii) any two from: all gases ; similar boiling points ; small molecules ; 2 2(a)(iii) feedstock for making chemicals ; 1 2(b)(i) family of compounds with, the same general formula ; similar chemical properties ; 2 2(b)(ii) C5H12 + 8O2 → 5CO2 + 6H2O formula ; balancing ; 2

2 (a) Fig. 2.1 shows a fractional distillation column used in the separation of petroleum. 400 °C 40 °C fractional distillation column fraction A fraction B hot petroleum Fig. 2.1 (i) Describe one similarity of the molecules in fraction A and fraction B. … … [1] (ii) Describe one difference between the molecules in fraction A and fraction B. … … [1] (b) Methane and propane are both members of the homologous series of alkanes. (i) State what is meant by a homologous series. … … … [2] (ii) Complete Fig. 2.2 to show the structure of a molecule of propane, C3H8. C C H Fig. 2.2 [2] (c) During the complete combustion of propane, carbon dioxide and water are formed. (i) Construct the balanced symbol equation for the complete combustion of propane. … [2] (ii) State one effect of an increase in the concentration of carbon dioxide in the atmosphere. … … [1] (iii) Draw a dot-and-cross diagram of a molecule of carbon dioxide. Show all of the outer shell electrons. [2] [Total: 11]

2(a)(i) molecules contain carbon and hydrogen (only) / are hydrocarbons / are covalent ; 1 2(a)(ii) fraction A molecules are smaller / have fewer carbon atoms / have lower intermolecular forces ; 1 2(b)(i) family of compounds with the same general formula ; similar chemical properties ; 2 2(b)(ii) 3 carbon atoms in chain ; all else correct ; 2 2(c)(i) C3H8 + 5O2 → 3CO2 + 4H2O ; correct formulae ; correctly balanced ; 2 2(c)(ii) global warming / climate change / consequence of climate change / enhanced greenhouse effect ; 1 2(c)(iii) two shared pairs of electrons between oxygen and carbon ; all else correct ; 2

2 (a) The formula of methanol is CH3OH. (i) State why methanol is not a hydrocarbon. … … [1] (ii) Complete the dot-and-cross diagram of a molecule of methanol. Show all of the atoms and all of the outer shell electrons. H C O [3] (b) (i) During the complete combustion of methanol, the amount of carbon dioxide in the air increases. Suggest one effect of this increase on the environment. … … [1] (ii) The products of the complete combustion of methanol are the same as the products of the complete combustion of hydrocarbons. Construct the balanced symbol equation for the complete combustion of methanol. State symbols are not required. … [3] [Total: 8]

2(a)(i) (methanol contains oxygen and) hydrocarbons contain only carbon atoms and hydrogen atoms ; 1 2(a)(ii) all hydrogen atoms correctly located ; correct electron distribution around carbon atom ; correct electron distribution around the oxygen atom ; 3 2(b)(i) enhanced greenhouse effect / global warming / climate change ; 1 2(b)(ii) 2CH3OH + 3O2 → 2CO2 + 4H2O correct formulae on LHS ; correct formulae on RHS ; correctly balanced ; 3

2 A student investigates the rate of reaction between calcium carbonate and dilute hydrochloric acid. The reaction produces carbon dioxide. Fig. 2.1 shows some of the apparatus that the student uses. calcium carbonate dilute hydrochloric acid Fig. 2.1 The student measures the volume of carbon dioxide produced every minute for 10 minutes. (a) Complete Fig. 2.1 to show the labelled apparatus that he uses to measure the volume of carbon dioxide produced. [2] (b) Fig. 2.2 shows the volume of carbon dioxide produced during the investigation. 0 1 2 3 4 5 time / minutes volume of carbon dioxide 6 7 8 9 10 Fig. 2.2 Describe and explain the change in the rate of the reaction during the first three minutes. Use ideas about concentration and particle collisions in your answer. change … explanation … … … [3] (c) Complete the balanced symbol equation for the reaction between dilute hydrochloric acid and calcium carbonate, CaCO3. … + … CaCl2 + … + … [2] (d) Describe the test for carbon dioxide and the positive result. test … result … [2] (e) Suggest the names of an acid and of a base that react together to produce magnesium sulfate. … and … [2]

2(a) draws a gas syringe or an inverted measuring cylinder over water ; syringe or measuring cylinder labelled ; 2 2(b) decreases ; concentration (of acid) decreases ; particles collide less often ; 3 2(c) 2HCl + (CaCO3 ) → (CaCl 2) + CO2 + H2O ;; 2 2(d) limewater ; (turns) milky / cloudy / white solid / ppt ; 2 2(e) (acid) sulfuric (acid) / H2SO4 ; (base) magnesium oxide / MgO / magnesium hydroxide / Mg(OH)2 / magnesium carbonate / MgCO3 ; 2 (a) To earn marks, you must draw either a gas syringe or an inverted measuring cylinder over water, and then label the apparatus correctly. (b) You need to state that the rate decreases, explain that the concentration of acid decreases, and then link this to particles colliding less often. (c) You must provide the correct balanced symbol equation: 2HCl + CaCO3 → CaCl2 + CO2 + H2O. (d) You need to name limewater and describe the color change as milky, cloudy, or a white solid/precipitate. (e) You must name sulfuric acid (H2SO4) as an acid and magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), or magnesium carbonate (MgCO3) as a base.

Cambridge IGCSE Combined Science · 0653

IGCSE Combined Science (0653) Stoichiometry past paper questions

Revise IGCSE Combined Science (0653) — Stoichiometry with real Cambridge past-paper questions grouped by topic, each shown with its marking scheme. Working one topic at a time targets exactly the skill each question tests.

22 free questions from 2016–2021, each with its marking scheme. Open the full topical bank to filter by subtopic, paper, and year.

Stoichiometry in IGCSE Combined Science 0653 exams, 2020–2025

Across 2020–2025, Stoichiometry accounted for 28 questions worth 81 marks in Cambridge IGCSE Combined Science (0653) papers.

By year
Year	Questions	Marks
2020	5	12
2021	3	3
2022	4	4
2023	5	13
2024	2	7
2025	9	42

Most-tested subtopics

C3.1 Formulas60 marks

Appears in

Paper 1 · 13 qs
Paper 2 · 8 qs
Paper 3 · 1 q
Paper 4 · 4 qs
Paper 6 · 2 qs

All most-tested Combined Science topics

2020 May/Jun · Paper 4 · Q2 · 8 marks
$2 The fractional distillation of petroleum is shown in Fig. 2.1. hot petroleum A … fraction B gasoline D … C naphtha E ……$ $2 The fractional distillation of petroleum is shown in Fig. 2.1. hot petroleum A … fraction B gasoline D … C naphtha E …… (continued)$
Marking scheme
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2019 Oct/Nov · Paper 4 · Q2 · 11 marks
$2 (a) Fig. 2.1 shows a fractional distillation column used in the separation of petroleum. 400 °C 40 °C fractional…$ $2 (a) Fig. 2.1 shows a fractional distillation column used in the separation of petroleum. 400 °C 40 °C fractional… (continued)$
Marking scheme
$Mark scheme: 2(a)(i) molecules contain carbon and hydrogen (only) / are hydrocarbons / are covalent ; 1 2(a)(ii) fraction A molecules are…$ Get Steven’s plain-English explanation
2019 Oct/Nov · Paper 4 · Q2 · 8 marks
Marking scheme
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2017 Feb/Mar · Paper 4 · Q2 · 11 marks
Marking scheme
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2021 Oct/Nov · Paper 1 · Q18 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q18
Answer: B
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