Carboxylic acids
Cambridge A-Level Chemistry (9701) · Unit 18: Carboxylic acids and derivatives · 7 flashcards
Carboxylic acids is topic 18.1 in the Cambridge A-Level Chemistry (9701) syllabus , positioned in Unit 18 — Carboxylic acids and derivatives , alongside Esters. In one line: Lithium aluminium hydride (LiAlH₄) in dry ether. Note: NaBH₄ is NOT strong enough to reduce carboxylic acids.
Marked as A2 Level: examined at A Level in Paper 4 (A Level Structured Questions) and Paper 5 (Planning, Analysis and Evaluation). It is not tested on the AS-only papers (Papers 1, 2 and 3).
The deck below contains 7 flashcards — 2 definitions, 3 key concepts and 2 calculations — covering the precise wording mark schemes reward. Use the 2 definition cards to lock down command-word answers (define, state), then move on to the concept and calculation cards to handle explain, describe, calculate and compare questions.
What reducing agent is used to reduce a carboxylic acid to a primary alcohol
Lithium aluminium hydride (LiAlH₄) in dry ether. Note: NaBH₄ is NOT strong enough to reduce carboxylic acids.
What the Cambridge 9701 syllabus says
2025-2027 syllabus, in our words · A2 LevelWhat the syllabus expects you to be able to do in this topic, in plain English. For the exact wording, see the official syllabus (PDF).
- Recall how carboxylic acids can be made: (a) oxidising primary alcohols or aldehydes by heating under reflux with acidified K₂Cr₂O₇ or acidified KMnO₄; (b) hydrolysing nitriles with dilute alkali or dilute acid, then acidifying; (c) heating esters with dilute alkali or dilute acid, then acidifying.
- Describe these reactions of carboxylic acids: (a) redox with reactive metals, giving a salt and H₂(g); (b) neutralisation by alkalis, giving a salt and H₂O(l); (c) acid-base reaction with carbonates, giving a salt, H₂O(l) and CO₂(g); (d) esterification with alcohols, catalysed by concentrated H₂SO₄; (e) reduction by LiAlH₄ to a primary alcohol.
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 9701 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Describe the reagents and conditions required to oxidise a primary alcohol to a carboxylic acid.
Acidified potassium dichromate (K₂Cr₂O₇) or acidified potassium manganate(VII) (KMnO₄) under reflux. The aldehyde intermediate is further oxidised to the carboxylic acid.
Write a balanced chemical equation for the reaction of ethanoic acid with sodium carbonate.
2CH₃COOH(aq) + Na₂CO₃(s) → 2CH₃COONa(aq) + H₂O(l) + CO₂(g)
What reagents and conditions are needed to hydrolyse a nitrile to a carboxylic acid?
Dilute acid (e.g. HCl) or dilute alkali (e.g. NaOH) under reflux, followed by acidification to protonate the carboxylate salt if alkali hydrolysis was used.
Describe the role of concentrated sulfuric acid in the esterification of a carboxylic acid with an alcohol.
Concentrated H₂SO₄ acts as a catalyst, increasing the rate of ester formation. It also removes water, shifting the equilibrium towards the ester product.
What reducing agent is used to reduce a carboxylic acid to a primary alcohol?
Lithium aluminium hydride (LiAlH₄) in dry ether. Note: NaBH₄ is NOT strong enough to reduce carboxylic acids.
Write a general equation representing the reaction of a carboxylic acid with a reactive metal.
2RCOOH(aq) + M(s) → (RCOO)₂M(aq) + H₂(g), where M is a reactive metal with a 2+ ion such as magnesium or zinc.
What are the products of the alkaline hydrolysis of an ester, before acidification?
The products are a carboxylate salt and an alcohol. Acidification is required to convert the salt into the carboxylic acid.
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Carboxylic acids sits alongside these A-Level Chemistry decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
Key terms covered in this Carboxylic acids deck
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