O Level Combined Science 5129 · Topic 22

Organic chemistry: past paper questions

104 real questionsasked in 10 of the last 10 exam series2019–2025usually: State, Name, Explain, Draw, Suggest

Real questions on organic chemistry

The newest 20 of 55 written questions, plus 49 multiple-choice. Open one to see it on the real paper.

5129/21 · October/November 2025 · Q5a[2]
State the name of hydrocarbon A and the name of hydrocarbon B. A
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5129/21 · October/November 2025 · Q5b[2]
Describe one similarity and one difference in the structures of A and B. similarity difference
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5129/21 · October/November 2025 · Q5c[1]
State a use for hydrocarbon A.
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5129/21 · October/November 2025 · Q5d[1]
Explain the meaning of the term ‘structural formula’.
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5129/21 · October/November 2025 · Q8d[1]
cracking
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5129/22 · October/November 2025 · Q5a(i)[1]
Balance the symbol equation for the reaction shown.
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5129/22 · October/November 2025 · Q5a(ii)[2]
State two conditions for cracking. condition
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5129/22 · October/November 2025 · Q5a(iii)[1]
State a use for hydrogen gas.
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5129/22 · October/November 2025 · Q5b[2]
Ethane and ethene can also be produced by the cracking of icosane. similarity difference Describe one similarity and one difference in the bonding in ethane and ethene.
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5129/22 · October/November 2025 · Q8c[1]
polymerisation
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5129/22 · May/June 2025 · Q8[4]
Petroleum is a of hydrocarbons. The bitumen fraction is used in making . The viscosity of the kerosene fraction is the viscosity of the bitumen fraction. The incomplete combustion of kerosene produces which Complete the sentences about petroleum.
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5129/22 · May/June 2025 · Q9b(i)[1]
State the name of the energy store that decreases as the hole is made.
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5129/21 · October/November 2024 · Q13b(ii)[1]
Name the fossil fuel that consists mainly of methane.
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5129/22 · October/November 2024 · Q12b(i)[1]
Draw the displayed formula of ethene, C 2 H 4 .
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5129/22 · October/November 2024 · Q12b(v)[1]
Draw a ring around the word that describes ethene. alkane alkene polymer saturated
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5129/21 · May/June 2024 · Q7e[1]
is a hydrocarbon.
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5129/22 · May/June 2024 · Q6c[1]
is an alkane
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5129/22 · October/November 2023 · Q6d(i)[1]
Suggest the name of a hydrocarbon that is chemical X.
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5129/22 · October/November 2023 · Q6d(iii)[1]
Suggest the name of a hydrocarbon that is chemical Z.
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5129/21 · May/June 2023 · Q8a[1]
Name one other fossil fuel that is not petroleum and is not obtained from petroleum.
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What examiners said

Only the most able candidates were familiar with the results of these hydrocarbon (alkane and alkene) reactions with aqueous bromine.
— Examiner report, October/November 2023, 5129/22 Q6(d)(i) (Cambridge)

Most candidates recalled that natural gas and coal are fossil fuels.
— Examiner report, May/June 2023, 5129/21 Q8(a) (Cambridge)

Very few candidates understood that the fractions in a fractionating column are separated by their different boiling points.
— Examiner report, May/June 2023, 5129/21 Q8(b)(i) (Cambridge)

Practise this topic

Answer these questions online and get each one marked against the official mark scheme, with what you missed and how to fix it.

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In the syllabus

22.1 Names and formulae of organic compounds

State that a structural formula is an unambiguous description of the way the atoms in a molecule are arranged
Draw and interpret the displayed formula of a molecule to show all the atoms and all the bonds
Name, draw and interpret the structural and displayed formulae of unbranched: (a) alkanes (b) alkenes containing up to three carbon atoms per molecule
State the type of compound present given the chemical name ending in –ane or -ene, or from a molecular, structural or displayed formula

22.2 Fuels

Name the fossil fuels: coal, natural gas and petroleum
Name methane as the main constituent of natural gas
State that hydrocarbons are compounds that contain hydrogen and carbon only
State that petroleum is a mixture of hydrocarbons
Describe the separation of petroleum into useful fractions by fractional distillation
Describe how the properties of fractions obtained from petroleum change as they are collected in a fractionating column from the bottom to the top of the column, limited to: (a) decreasing chain length (b) higher volatility (c) higher flammability (d) lower boiling points (e) lower viscosity
Name the uses of the fractions as: (a) refinery gas fraction for gas used for heating and cooking (b) gasoline/petrol fraction for fuel used in cars (c) naphtha fraction as a chemical feedstock (d) kerosene/paraffin fraction for jet fuel (e) diesel oil / gas oil fraction for fuel used in diesel engines (f) fuel oil fraction for fuel used in ships and home heating systems (g) lubricating oil fraction for lubricants, waxes and polishes (h) bitumen fraction for making roads

22.3 Alkanes

State that the bonding in alkanes is single covalent and that alkanes are saturated hydrocarbons
Describe the properties of alkanes as being generally unreactive, except in terms of combustion

22.4 Alkenes

State that the bonding in alkenes includes a double carbon–carbon covalent bond and that alkenes are unsaturated hydrocarbons
Describe the manufacture of alkenes and hydrogen by the cracking of large alkane molecules using a high temperature, and a catalyst
Describe the reasons for the cracking of large alkane molecules
Describe the test to distinguish between saturated and unsaturated hydrocarbons by their reaction with aqueous bromine
State that in an addition reaction only one product is formed
Describe the formation of poly(ethene) from ethene by addition polymerisation, identifying the repeat unit
State that poly(ethene) is a widely used plastic

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