OCR GCSE Chemistry A: Organic chemistry (J248) – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover sub-topic C6.2 Organic chemistry in J248, the OCR GCSE (9–1) Chemistry A (Gateway Science) specification (Version 4.0, August 2026): learning outcomes C6.2a to C6.2q, the mathematical learning outcome CM6.2i and the practical suggestions on models and making nylon. Two questions test C6.2e and C6.2f and carry a Higher Tier only label; Foundation and Higher candidates can attempt the rest. Topic C6 sits on Paper 2 at Foundation Tier and on Paper 4 at Higher Tier.

Find other J248 topics through the chemistry hub for OCR GCSE; each statement appears on a printable checklist for J248. Relative atomic masses where needed: H = 1, C = 12, O = 16, F = 19.

Questions

1. Here are four organic compounds: C₃H₆, C₂H₅COOH, C₄H₉OH, C₅H₁₂.

(a) Name the homologous series of each compound. [2] (b) Give the functional group of the alcohol. [1]

2. This question is about naming, drawing and shape.

(a) Name the compound CH₃CH₂CH₂COOH. [1] (b) Draw the displayed formula of propan-1-ol. [2] (c) The displayed formula of methane shows H–C–H angles of 90°. State the actual shape and approximate angle of a methane molecule. [2]

3. Heptane, C₇H₁₆, is a fuel found in petrol.

(a) Heptane burns completely in oxygen. Write the balanced symbol equation. [2] (b) Calculate the mass of carbon dioxide formed when 5.00 g of heptane burns completely. [2]

4. But-1-ene, CH₂=CHCH₂CH₃, reacts with bromine and with hydrogen.

(a) Describe what you would see when but-1-ene is shaken with bromine water. [1] (b) Give the molecular formula of the product with bromine. [1] (c) Name the product with hydrogen, and state the catalyst used. [2] (d) Name the type of reaction in (b) and (c). [1]

5. A student warms butan-1-ol with acidified potassium manganate(VII) solution.

(a) State the colour change. [1] (b) Name the organic product and give its formula. [2] (c) The student predicts that pentan-1-ol will react the same way. Explain why this prediction is reasonable. [1]

6. Fluoroethene, CH₂=CHF, forms an addition polymer.

(a) Draw the repeat unit of poly(fluoroethene), using the [repeat unit]ₙ form. [2] (b) A chain of poly(fluoroethene) has Mr 92 000. Calculate the number of monomers in the chain. [2] (c) A different polymer has the repeat unit –[CH(CH₃)–CH(CH₃)]–. Give the structural formula and name of its monomer. [2]

7. Higher Tier only. A polyester is made from monomer A, HO–●–OH, and monomer B, HOOC–■–COOH, where the blocks stand for carbon chains.

(a) Name the small molecule formed with the polymer. [1] (b) Draw a block diagram of the repeat unit. [2] (c) Explain why monomer A must have two –OH groups, not one. [1] (d) A long polyester chain grows by a further 400 repeat units. State how many small molecules form as it does so. [1]

8. Higher Tier only. Describe how nylon can be made in the laboratory from 1,6-diaminohexane solution and hexanedioyl dichloride solution. Include the small molecule formed and one safety precaution. [4]

9. Living things contain natural polymers.

(a) Name the monomers that make up DNA. [1] (b) Name the four bases that identify these monomers. [1] (c) Name the type of monomer used to build (i) proteins and (ii) starch. [2]

10. Crude oil is separated by fractional distillation.

(a) Explain why the fraction collected at the bottom of the column has a higher boiling point than the fraction collected at the top. Refer to molecular size and forces. [3] (b) Give the general formula of most compounds in the fractions. [1] (c) Explain why crude oil is described as a finite resource. [1] (d) State one use of crude oil other than as a fuel. [1]

11. The table shows illustrative supply and demand data for a refinery.

Fraction	Supply from distillation / %	Demand / %
Refinery gases	4	5
Petrol	10	26
Kerosene	12	9
Diesel	20	25
Fuel oil and bitumen	54	35

(a) Explain, using figures from the table, why some fuel oil is cracked at this refinery. [2] (b) Dodecane is cracked: C₁₂H₂₆ → C₆H₁₄ + C₄H₈ + X. Identify X. [1] (c) State the conditions used for catalytic cracking. [2] (d) Describe a test to show that the cracked products contain an alkene. [1]

12. A delivery company is choosing between hydrogen/oxygen fuel cells and rechargeable batteries for its vans.

(a) Write the overall equation for the reaction in a hydrogen/oxygen fuel cell. [1] (b) Write the half equation at the negative electrode when the electrolyte is acidic. [1] (c) Explain why a rechargeable battery must be recharged, but a fuel cell does not stop working. [1] (d) A van uses 0.60 kg of hydrogen on one trip. Calculate the mass of water produced. [2] (e) Evaluate the use of fuel cells for the vans. [2]

Answers

1. (a) C₃H₆ alkene; C₂H₅COOH carboxylic acid [1]; C₄H₉OH alcohol; C₅H₁₂ alkane [1]. (b) –OH (hydroxyl) [1] Examiner insight: For the hydrocarbons, test the hydrogen count against 2n and 2n + 2; guessing from molecule size makes C₃H₆ and C₅H₁₂ easy to mix up.

2. (a) Butanoic acid [1] (b) Three carbons in a chain with all C–H and C–C bonds shown [1]; O–H on the end carbon, drawn as C–O–H with both bonds visible [1]. (c) Tetrahedral [1]; about 109.5° [1]. Examiner insight: In (b), writing –OH as a group without the O–H bond is a condensed formula, not a displayed one; show every bond.

3. (a) Correct formulae of products, CO₂ and H₂O [1]; C₇H₁₆ + 11O₂ → 7CO₂ + 8H₂O [1] (b) Mr = 100, so 5.00 ÷ 100 = 0.0500 mol; CO₂ = 7 × 0.0500 = 0.350 mol [1]; 0.350 × 44 = 15.4 g [1] Examiner insight: Use the 1 : 7 ratio from your equation; a 1 : 1 ratio gives 2.20 g, which shows a working step was missed.

4. (a) Orange bromine water turns colourless [1]. (b) C₄H₈Br₂ (1,2-dibromobutane) [1] (c) Butane [1]; nickel catalyst [1]. (d) Addition [1] Examiner insight: “Clear” describes transparency, not colour; write colourless to describe the change.

5. (a) Purple to colourless [1] (b) Butanoic acid [1]; C₃H₇COOH [1] (c) Pentan-1-ol has the same –OH functional group, and the functional group decides the reaction [1]. Examiner insight: The acid keeps all four carbons; naming propanoic acid suggests a carbon was lost, which oxidation does not do here.

6. (a) Single C–C bond between two carbons, with H, H, H and F on them [1]; brackets with bonds through them and n outside [1]. (b) Mr of C₂H₃F = 24 + 3 + 19 = 46 [1]; 92 000 ÷ 46 = 2000 [1] (c) CH₃CH=CHCH₃ [1]; but-2-ene [1]. Examiner insight: In (c), put the double bond between the two main-chain carbons of the repeat unit; drawing it elsewhere gives a monomer that would make a different polymer.

7. (a) Water [1] (b) Repeat unit –[O–●–O–OC–■–CO]– [1], with brackets and n [1]. (c) One –OH joins the chain on one side and the second joins it on the other; with one, the chain stops [1]. (d) Each new repeat unit adds two ester links, so 800 water molecules [1]. Examiner insight: In (b), check that each block keeps its own atoms: ● keeps both O atoms and ■ keeps both C=O groups.

8. Diamine solution in water in a beaker, with the dichloride solution (in cyclohexane) poured gently on top as a separate layer [1]. Nylon forms at the boundary between the layers [1]; it is lifted with tweezers and wound slowly onto a rod [1]. Small molecule hydrogen chloride, plus one precaution: gloves/eye protection (corrosive reagents) or no naked flames (flammable cyclohexane) [1]. Examiner insight: Say the layers must not be mixed; describing stirring the two solutions together loses the key step of the method.

9. (a) Nucleotides [1] (b) Adenine, thymine, cytosine, guanine [1] (c) (i) Amino acids [1]; (ii) sugars, such as glucose [1]. Examiner insight: “Bases” alone is not the monomer; the monomers are nucleotides, named after their bases.

10. (a) Bottom fraction has larger molecules [1]; larger molecules have stronger intermolecular forces [1]; overcoming them takes more energy, which raises the boiling point [1]. (b) CₙH₂ₙ₊₂ (alkanes) [1] (c) It formed over millions of years and is being used much faster than it forms [1]. (d) Any one: feedstock for plastics, solvents, detergents or medicines [1]. Examiner insight: Name intermolecular forces; an answer about breaking covalent bonds describes cracking, not boiling.

11. (a) Fuel oil and bitumen supply (54%) exceeds demand (35%) [1]; petrol demand (26%) exceeds supply (10%), so cracking turns surplus long chains into shorter, more wanted molecules [1]. (b) C₂H₄ (ethene) [1] (c) Vaporised alkane passed over a hot catalyst [1]; about 500 °C with a zeolite catalyst [1]. (d) Shake with bromine water; it turns from orange to colourless [1]. Examiner insight: Quote figures from the table for both the surplus and the shortage; a general statement about demand does not use the data.

12. (a) 2H₂ + O₂ → 2H₂O [1] (b) H₂ → 2H⁺ + 2e⁻ [1] (c) A battery’s reactants are used up, but a fuel cell is supplied with fresh fuel and oxygen continuously [1]. (d) 600 ÷ 2 = 300 mol H₂, giving 300 mol H₂O [1]; 300 × 18 = 5400 g = 5.4 kg [1]. (e) For: refuelling is quick and the only product at the van is water [1]. Against: hydrogen is hard to store safely and may be made from fossil fuels, with few filling stations; judgement, e.g. suitable only if the depot has its own hydrogen supply [1]. Examiner insight: In (d), convert 0.60 kg to grams before dividing by Mr; 0.60 ÷ 2 gives a value a thousand times too small.

Where marks are usually lost

• Using C₃H₇OH-style formulae where a displayed formula is asked for.
• Leaving the –COOH carbon out of a carboxylic acid’s name.
• Combustion equations with the products right but the oxygen unbalanced.
• Writing “clear” instead of colourless for bromine water.
• Forgetting the nickel catalyst for hydrogen addition.
• Keeping a double bond inside an addition polymer’s repeat unit.
• (Higher Tier) Saying water forms in the nylon rope trick, when the dichloride gives hydrogen chloride.
• Explaining boiling point with covalent bonds instead of intermolecular forces.
• Giving only “heat” for cracking conditions, without the catalyst.
• Not converting kilograms to grams in a moles calculation.

Next steps

• C6.2 organic chemistry study guide
• All free 10-minute diagnostics
• C6.2 organic chemistry revision notes
• Book a free trial class
• J248 checklist to print and tick
• Every J248 topic on the hub

Official syllabus

Published by OCR: Version 4.0 (August 2026) of specification J248, for the GCSE (9–1) in Chemistry A, Gateway Science, first assessed in 2018. Content taken from it: sub-topic C6.2 Organic chemistry, statements C6.2a–C6.2q, maths outcome CM6.2i, and the practical suggestions “Use of models” and “Making nylon”.