2 (a) Magnesium is in Period 3 of the Periodic Table. (i) Use the Periodic Table to name the noble gas in Period 3 of the Periodic Table. … [1] (ii) Describe the change in metallic character across Period 3. … … [1] (b) Magnesium reacts with carbon dioxide. Magnesium oxide and carbon are made. (i) Write the word equation for this reaction. … + … … + … [1] (ii) The reaction between magnesium and carbon dioxide is exothermic. Explain what is meant by an exothermic reaction. … … [1] (c) An atom of magnesium has a proton number (atomic number) of 12 and a nucleon number (mass number) of 24. Complete Table 2.1 to show the names and numbers of the two particles contained in the nucleus of this magnesium atom. Table 2.1 name of particle number of particles [2] (d) Magnesium carbonate reacts with dilute hydrochloric acid to make aqueous magnesium chloride. (i) Magnesium carbonate is insoluble in water. State the separation technique used to remove magnesium carbonate from a mixture of magnesium carbonate and water. … [1] (ii) Magnesium chloride dissolves in water. State the separation technique used to obtain solid magnesium chloride from a solution of magnesium chloride. … [1] (iii) Magnesium carbonate reacts with dilute hydrochloric acid. Complete the balanced symbol equation for this reaction. MgCO3 + …HCl MgCl 2 + CO2 + H2O [1] (iv) Dilute hydrochloric acid contains aqueous chloride ions. State the test for aqueous chloride ions and give the observation for a positive result. test … observation … [2] (e) Table 2.2 shows the composition of a magnesium alloy. Table 2.2 element % by mass magnesium 94 neodymium 2 yttrium 4 (i) Calculate the mass of magnesium in 500 kg of the alloy. … kg [1] (ii) The alloy is used in aircraft bodies. Suggest why the alloy of magnesium is used rather than pure magnesium for aircraft bodies. … … [1] [Total: 13]

2(a)(i) argon ; 1 2(a)(ii) metal to non-metal ; 1 2(b)(i) magnesium + carbon dioxide → carbon + magnesium oxide ; 1 2(b)(ii) thermal energy released ; 1 2(c) protons –12 ; neutrons –12 ; 2 2(d)(i) filtration ; 1 2(d)(ii) crystallisation ; 1 2(d)(iii) MgCO3 + 2HCl → MgCl2 + CO2 + H2O ; 1 2(d)(iv) (acidified) (aqueous) silver nitrate ; white precipitate ; 2 2(e)(i) 470 (kg) ; 1 2(e)(ii) stronger / less dense ; 1 (a)(i) To earn this mark, you must correctly identify 'argon' as the noble gas in Period 3. (a)(ii) To earn this mark, you must describe the change in metallic character across Period 3 as going from 'metal to non-metal'. (b)(i) To earn this mark, you must write the correct word equation: 'magnesium + carbon dioxide → carbon + magnesium oxide'. (b)(ii) To earn this mark, you must explain that an exothermic reaction is one where 'thermal energy is released'. (c) To earn these two marks, you must correctly state that the nucleus contains 'protons – 12' and 'neutrons – 12'. (d)(i) To earn this mark, you must identify 'filtration' as the correct separation technique. (d)(ii) To earn this mark, you must identify 'crystallisation' as the correct separation technique. (d)(iii) To earn this mark, you must write the correct balanced chemical equation: 'MgCO3 + 2HCl → MgCl2 + CO2 + H2O'. (d)(iv) To earn these two marks, you must state the use of '(acidified) (aqueous) silver nitrate' and observe a 'white precipitate'. (e)(i) To earn this mark, you must state the correct value '470 (kg)'. (e)(ii) To earn this mark, you must state that the alloy is 'stronger / less dense' than pure magnesium.

2 (a) Magnesium is in Period 3 of the Periodic Table. (i) Use the Periodic Table to name the noble gas in Period 3 of the Periodic Table. … [1] (ii) Describe the change in metallic character across Period 3. … … [1] (b) Magnesium reacts with carbon dioxide. Magnesium oxide and carbon are made. (i) Write the word equation for this reaction. … + … … + … [1] (ii) The reaction between magnesium and carbon dioxide is exothermic. Explain what is meant by an exothermic reaction. … … [1] (c) An atom of magnesium has a proton number (atomic number) of 12 and a nucleon number (mass number) of 24. Complete Table 2.1 to show the names and numbers of the two particles contained in the nucleus of this magnesium atom. Table 2.1 name of particle number of particles [2] (d) Magnesium carbonate reacts with dilute hydrochloric acid to make aqueous magnesium chloride. (i) Magnesium carbonate is insoluble in water. State the separation technique used to remove magnesium carbonate from a mixture of magnesium carbonate and water. … [1] (ii) Magnesium chloride dissolves in water. State the separation technique used to obtain solid magnesium chloride from a solution of magnesium chloride. … [1] (iii) Magnesium carbonate reacts with dilute hydrochloric acid. Complete the balanced symbol equation for this reaction. MgCO3 + …HCl MgCl 2 + CO2 + H2O [1] (iv) Dilute hydrochloric acid contains aqueous chloride ions. State the test for aqueous chloride ions and give the observation for a positive result. test … observation … [2] (e) Table 2.2 shows the composition of a magnesium alloy. Table 2.2 element % by mass magnesium 94 neodymium 2 yttrium 4 (i) Calculate the mass of magnesium in 500 kg of the alloy. … kg [1] (ii) The alloy is used in aircraft bodies. Suggest why the alloy of magnesium is used rather than pure magnesium for aircraft bodies. … … [1] [Total: 13]

2(a)(i) argon ; 1 2(a)(ii) metal to non-metal ; 1 2(b)(i) magnesium + carbon dioxide → carbon + magnesium oxide ; 1 2(b)(ii) thermal energy released ; 1 2(c) protons –12 ; neutrons –12 ; 2 2(d)(i) filtration ; 1 2(d)(ii) crystallisation ; 1 2(d)(iii) MgCO3 + 2HCl → MgCl2 + CO2 + H2O ; 1 2(d)(iv) (acidified) (aqueous) silver nitrate ; white precipitate ; 2 2(e)(i) 470 (kg) ; 1 2(e)(ii) stronger / less dense ; 1 (a)(i) To earn this mark, you must correctly identify 'argon' as the noble gas in Period 3. (a)(ii) To earn this mark, you must describe the change in metallic character across Period 3 as going from 'metal to non-metal'. (b)(i) To earn this mark, you must write the correct word equation: 'magnesium + carbon dioxide → carbon + magnesium oxide'. (b)(ii) To earn this mark, you must explain that an exothermic reaction is one where 'thermal energy is released'. (c) To earn these two marks, you must correctly state that the nucleus contains 'protons – 12' and 'neutrons – 12'. (d)(i) To earn this mark, you must identify 'filtration' as the correct separation technique. (d)(ii) To earn this mark, you must identify 'crystallisation' as the correct separation technique. (d)(iii) To earn this mark, you must write the correct balanced chemical equation: 'MgCO3 + 2HCl → MgCl2 + CO2 + H2O'. (d)(iv) To earn these two marks, you must state the use of '(acidified) (aqueous) silver nitrate' and observe a 'white precipitate'. (e)(i) To earn this mark, you must state the correct value '470 (kg)'. (e)(ii) To earn this mark, you must state that the alloy is 'stronger' or 'less dense' than pure magnesium.

5 (a) Potassium is a very reactive metal. Potassium is stored under oil as shown in Fig. 5.1. potassium oil pieces of potassium Fig. 5.1 Suggest two reasons why potassium is stored under oil. 1 … 2 … [2] (b) Potassium has a proton number of 19. Complete Fig. 5.2 to show the electronic structure of a potassium atom. The inner shell electrons have been drawn for you. Fig. 5.2 [2] (c) Solid potassium reacts with chlorine gas to make solid potassium chloride. (i) Describe the differences between the structures of a solid and a gas in terms of particle separation and particle arrangement. particle separation … … particle arrangement … … [2] (ii) When potassium reacts with chlorine, potassium atoms become potassium ions. Describe what happens to a potassium atom when it becomes a potassium ion. … [1] (iii) Potassium and chlorine are elements. Potassium chloride is a compound. Describe the difference between an element and a compound. … … … [2] (d) The maximum mass of potassium chloride that dissolves in 100 cm3 of water is called the solubility of potassium chloride. Fig. 5.3 shows the solubility of potassium chloride in water at different temperatures. 0 10 20 30 40 50 60 70 10 20 30 40 50 temperature / °C solubility g / 100 cm3 of water 60 70 80 90 100 Fig. 5.3 (i) Describe the trend in solubility shown in Fig. 5.3. … [1] (ii) State the mass of potassium chloride that dissolves in 100 cm3 of water at 45 °C. …g [1] [Total: 11]

5(a) to prevent potassium reacting (with) ; air / oxygen / water vapour ; 2 5(b) 19 electrons shown ; (2).8.8.1 ; 2 5(c)(i) particle separation - further apart in a gas / touching / close in a solid) ; particle arrangement – regular arrangement in solid / random arrangement in gas ; 2 5(c)(ii) loses one electron ; 1 5(c)(iii) an element contains only one type of atom ; a compound contains two or more elements / different atoms chemically combined ; 2 5(d)(i) solubility increases as temperature rises ; 1 5(d)(ii) 41 g ; (± 1) 1 (a) To earn these two marks, you must state that potassium is stored under oil to prevent it from reacting with 'air / oxygen / water vapour'. (b) To earn these two marks, you must show 19 electrons in total and correctly draw the electronic structure as (2).8.8.1. (c)(i) To earn these two marks, you must describe particle separation as 'further apart in a gas / touching / close in a solid' and particle arrangement as 'regular arrangement in solid / random arrangement in gas'. (c)(ii) To earn this mark, you must state that potassium atoms 'lose one electron' to become potassium ions. (c)(iii) To earn these two marks, you must define an element as containing 'only one type of atom' and a compound as containing 'two or more elements / different atoms chemically combined'. (d)(i) To earn this mark, you must state that 'solubility increases as temperature rises'. (d)(ii) To earn this mark, you must correctly read the value '41 g' (within ±1) from the graph.

5 (a) Potassium is a very reactive metal. Potassium is stored under oil as shown in Fig. 5.1. potassium oil pieces of potassium Fig. 5.1 Suggest two reasons why potassium is stored under oil. 1 … 2 … [2] (b) Potassium has a proton number of 19. Complete Fig. 5.2 to show the electronic structure of a potassium atom. The inner shell electrons have been drawn for you. Fig. 5.2 [2] (c) Solid potassium reacts with chlorine gas to make solid potassium chloride. (i) Describe the differences between the structures of a solid and a gas in terms of particle separation and particle arrangement. particle separation … … particle arrangement … … [2] (ii) When potassium reacts with chlorine, potassium atoms become potassium ions. Describe what happens to a potassium atom when it becomes a potassium ion. … [1] (iii) Potassium and chlorine are elements. Potassium chloride is a compound. Describe the difference between an element and a compound. … … … [2] (d) The maximum mass of potassium chloride that dissolves in 100 cm3 of water is called the solubility of potassium chloride. Fig. 5.3 shows the solubility of potassium chloride in water at different temperatures. 0 10 20 30 40 50 60 70 10 20 30 40 50 temperature / °C solubility g / 100 cm3 of water 60 70 80 90 100 Fig. 5.3 (i) Describe the trend in solubility shown in Fig. 5.3. … [1] (ii) State the mass of potassium chloride that dissolves in 100 cm3 of water at 45 °C. …g [1] [Total: 11]

5(a) to prevent potassium reacting (with) ; air / oxygen / water vapour ; 2 5(b) 19 electrons shown ; (2).8.8.1 ; 2 5(c)(i) particle separation - further apart in a gas / touching / close in a solid) ; particle arrangement – regular arrangement in solid / random arrangement in gas ; 2 5(c)(ii) loses one electron ; 1 5(c)(iii) an element contains only one type of atom ; a compound contains two or more elements / different atoms chemically combined ; 2 5(d)(i) solubility increases as temperature rises ; 1 5(d)(ii) 41 g ; (± 1) 1 (a) To earn these two marks, you must state that potassium is stored under oil to prevent it from reacting with 'air / oxygen' and 'water vapour'. (b) To earn these two marks, you must show 19 electrons in total and correctly draw the electronic structure as 2.8.8.1. (c)(i) To earn these two marks, you must describe particle separation as 'further apart in a gas / touching / close in a solid' and particle arrangement as 'regular arrangement in solid / random arrangement in gas'. (c)(ii) To earn this mark, you must state that a potassium atom 'loses one electron' to become an ion. (c)(iii) To earn these two marks, you must define an element as containing 'only one type of atom' and a compound as containing 'two or more elements / different atoms chemically combined'. (d)(i) To earn this mark, you must state that 'solubility increases as temperature rises'. (d)(ii) To earn this mark, you must correctly read the value '41 g' (within ±1) from the graph.

Cambridge IGCSE Co-ordinated Sciences · 0654

IGCSE Co-ordinated Sciences (0654) Stoichiometry past paper questions

Revise IGCSE Co-ordinated Sciences (0654) — 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.

69 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 Co-ordinated Sciences 0654 exams, 2020–2025

Across 2020–2025, Stoichiometry accounted for 138 questions worth 1,079 marks in Cambridge IGCSE Co-ordinated Sciences (0654) papers.

By year
Year	Questions	Marks
2020	20	156
2021	18	145
2022	25	178
2023	21	171
2024	28	240
2025	26	189

Most-tested subtopics

C3.3 The mole and the Avogadro constant600 marks
C3.1 Formulas501 marks
C3.2 Relative masses of atoms and molecules124 marks

Appears in

Paper 1 · 9 qs
Paper 2 · 30 qs
Paper 3 · 27 qs
Paper 4 · 61 qs
Paper 5 · 5 qs
Paper 6 · 6 qs

All most-tested Co-ordinated Sciences topics

2021 May/Jun · Paper 3 · Q2 · 13 marks
Marking scheme
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2021 May/Jun · Paper 3 · Q2 · 13 marks
Marking scheme
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2021 May/Jun · Paper 3 · Q5 · 11 marks
Marking scheme
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2021 May/Jun · Paper 3 · Q5 · 11 marks
Marking scheme
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2021 Feb/Mar · Paper 1 · Q15 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q15
Answer: C
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