1 (a) A list of formulae is shown. CaCO3 CaO Cl 2 CH4 C2H5OH C2H6 CuSO4 H2 H2O MgO NaCl SO2 Answer the following questions using these formulae. Each formula may be used once, more than once or not at all. State which formula represents: (i) a compound that is the main constituent of natural gas … [1] (ii) an element that is used in water treatment … [1] (iii) an element that bleaches damp litmus paper … [1] (iv) a compound that contains an ion with a single negative charge … [1] (v) a hydrocarbon that is formed by the decomposition of vegetation. … [1] (b) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of water. H H O [2] (c) State whether calcium oxide is a basic oxide or an acidic oxide. Give a reason for your answer. … … [1] [Total: 8]

1(a)(i) CH4 1 1(a)(ii) Cl 2 1 1(a)(iii) Cl 2 1 1(a)(iv) NaCl 1 1(a)(v) CH4 1 1(b) bonding pair of electrons between each H and O atom and no other electrons on H atoms (1) four non-bonding electrons on the oxygen atom (1) 2 1(c) basic (oxide) AND calcium is a metal / metal oxides are basic (1) 1 (a) To earn marks, you must correctly identify the chemical formula for each description from the provided list. (b) To earn marks, you must draw a dot-and-cross diagram showing one bonding pair of electrons between each hydrogen and oxygen atom, with no other electrons on the hydrogen atoms, and four non-bonding electrons on the oxygen atom. (c) To earn the mark, you must state that calcium oxide is a basic oxide and provide the reason that calcium is a metal or that metal oxides are basic.

1 (a) A list of formulae is shown. Br2 CO CO2 CH4 C2H6 HCl KBr LiCl MgCl 2 O2 SO2 Answer the following questions using these formulae. Each formula may be used once, more than once or not at all. State which formula represents: (i) a compound that gives a red colour in a flame test … [1] (ii) a compound containing an ion with a 2+ charge … [1] (iii) a compound that is a product of respiration … [1] (iv) a compound used as a food preservative … [1] (v) an element that is used in the production of steel. … [1] (b) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of hydrogen chloride. Show outer shell electrons only. Cl H [2] (c) State whether carbon dioxide is a basic oxide or an acidic oxide. Give a reason for your answer. … … [1] [Total: 8]

1(a)(i) LiCl 1 1(a)(ii) MgCl2 1 1(a)(iii) CO2 1 1(a)(iv) SO2 1 1(a)(v) O2 1 1(b) bonding pair of electrons between the Cl atom and H atom and no other electrons on hydrogen atom (1) 6 non-bonding electrons on Cl atom (1) 2 1(c) acidic (oxide) AND carbon is a non-metal / non-metal oxides are acidic (1) 1 (a) To earn marks, you must correctly identify the specific chemical formula from the provided list for each description. (b) For the first mark, draw a single bonding pair of electrons between H and Cl, ensuring no other electrons are on the hydrogen atom. For the second mark, show six non-bonding electrons (three lone pairs) on the chlorine atom. (c) You must state that carbon dioxide is an acidic oxide AND provide the reason that carbon is a non-metal or that non-metal oxides are acidic.

2 The table shows the masses of some of the ions in 1000 cm3 of rainwater. name of ion formula of ion mass of ion in 1000 cm3 of rainwater / mg NH4 + 0.08 calcium Ca2+ 0.13 chloride Cl – 1.30 magnesium Mg2+ 0.08 nitrate NO3 – 0.70 potassium K+ 0.08 sodium Na+ 0.80 SO4 2– 1.60 (a) Answer these questions using only the information in the table. (i) State which of the positive ions has the highest concentration. … [1] (ii) Name the compound containing NH4 + and SO4 2– ions. … [1] (iii) Calculate the mass of magnesium ions in 400 cm3 of rainwater. mass = … mg [1] (b) Describe a test for chloride ions. test … observations … [2] (c) Small amounts of carboxylic acids are also present in rainwater. The structure of tartaric acid is shown. C H H O C C O O O H C H H O O H (i) On the structure draw a circle around one alcohol functional group. [1] (ii) Deduce the formula of tartaric acid to show the number of carbon, hydrogen and oxygen atoms. … [1] (d) Tartaric acid can be converted into compound A. The formula of compound A is C3H4O3. Complete the table to calculate the relative molecular mass of compound A. type of atom number of atoms relative atomic mass carbon 3 12 3 × 12 = 36 hydrogen 1 oxygen 16 relative molecular mass = … [2] [Total: 9]

2(a)(i) Na+ 1 2(a)(ii) ammonium sulfate 1 2(a)(iii) 0.032 (mg) 1 2(b) (acidified aqueous) silver nitrate (1) white precipitate (1) 2 2(c)(i) OH group attached to 2nd or 3rd C atoms circled (1) 1 2(c)(ii) C4H6O6 1 2(d) 88 (2) if two marks nor scored, 1 mark for 4 × 1 = 4 OR 3 × 16 = 48 2 (a)(i) To earn this mark, you must correctly identify Na+ as the positive ion with the highest concentration. (a)(ii) To earn this mark, you must correctly name the compound as ammonium sulfate. (a)(iii) To earn this mark, you must correctly calculate the mass of magnesium ions as 0.032 mg. (b) To earn the first mark, you must state that the test involves adding (acidified aqueous) silver nitrate. To earn the second mark, you must state that the observation is a white precipitate. (c)(i) To earn this mark, you must circle an OH group attached to the second or third carbon atom in the given structure. (c)(ii) To earn this mark, you must correctly deduce the formula of tartaric acid as C4H6O6. (d) To earn two marks, you must correctly calculate the relative molecular mass as 88. If two marks are not scored, you can earn one mark for correctly calculating 4 × 1 = 4 OR 3 × 16 = 48.

2 The table shows the masses of some of the ions in 1000 cm3 of water taken from a lake. name of ion formula of ion mass of ion in 1000 cm3 of lake water / mg calcium Ca2+ 0.41 chloride Cl – 4.40 magnesium Mg2+ 0.39 NO3 – 0.03 potassium K+ 0.30 silicate SiO3 2– 0.02 Na+ 2.90 sulfate SO4 2– 2.80 (a) Answer these questions using only the information in the table. (i) State which of the negative ions has the lowest concentration. … [1] (ii) Name the compound containing Na+ and NO3 – ions. … [1] (iii) Calculate the mass of chloride ions in 250 cm3 of lake water. mass = … mg [1] (b) Describe a test for sulfate ions. test … observations … [2] (c) Citric acid is also present in the lake water. The structure of citric acid is shown. O O H O C C C C C C H H O O O O H H H H H (i) Deduce the number of carboxylic acid groups in one molecule of citric acid. … [1] (ii) The formula of citric acid is C6H8O7. Complete the table to calculate the relative molecular mass of citric acid. type of atom number of atoms relative atomic mass carbon 6 12 6 × 12 = 72 hydrogen 1 oxygen 16 relative molecular mass = … [2] [Total: 8]

2(a)(i) SiO32- 1 2(a)(ii) sodium nitrate 1 2(a)(iii) 1.10 / 1.1 (mg) 1 2(b) (acidified aqueous) barium nitrate (1) white precipitate (1) 2 2(c)(i) 3 (1) 1 2(c)(ii) 192 (2) if two marks not scored, 1 mark for 8 × 1 = 8 OR 7 × 16 = 112 2 (a) To earn marks, you must correctly identify the negative ion with the lowest concentration, name the compound formed from Na+ and NO3- ions, and calculate the mass of chloride ions in 250 cm3 of lake water. (b) To earn marks, you must describe the test for sulfate ions by stating the reagent (acidified aqueous barium nitrate) and the expected observation (white precipitate). (c) To earn the mark, you must correctly deduce the number of carboxylic acid groups in one molecule of citric acid. For the second part, you must calculate the correct relative molecular mass; partial credit is given for correctly calculating the total mass of hydrogen or oxygen atoms.

Cambridge IGCSE Chemistry · 0620

IGCSE Chemistry (0620) Organic chemistry past paper questions

Organic questions test homologous series, functional groups, their reactions, and polymers.

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

Organic chemistry in IGCSE Chemistry 0620 exams, 2020–2025

Across 2020–2025, Organic chemistry accounted for 824 questions worth 2,583 marks in Cambridge IGCSE Chemistry (0620) papers.

By year
Year	Questions	Marks
2020	133	414
2021	150	447
2022	153	457
2023	125	390
2024	134	429
2025	129	446

Most-tested subtopics

11.1 Formulae, functional groups and terminology1287 marks
11.4 Alkenes1034 marks
11.5 Alcohols1020 marks

Appears in

Paper 1 · 307 qs
Paper 2 · 339 qs
Paper 3 · 87 qs
Paper 4 · 80 qs
Paper 5 · 2 qs
Paper 6 · 9 qs

All most-tested Chemistry topics

2021 Oct/Nov · Paper 3 · Q1 · 8 marks
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2021 Oct/Nov · Paper 3 · Q1 · 8 marks
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2021 Oct/Nov · Paper 3 · Q2 · 9 marks
Marking scheme
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2021 Oct/Nov · Paper 3 · Q2 · 8 marks
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2021 Oct/Nov · Paper 1 · Q12 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q12
Answer: B
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