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
Official 2025-2027 spec · A2 LevelThese are the exact learning outcomes Cambridge sets for this topic. The candidate is expected to be able to do each of these on the relevant paper.
- recall the reactions by which carboxylic acids can be produced: (a) oxidation of primary alcohols and aldehydes with acidified K2Cr2O7 or acidified KMnO4 and refluxing (b) hydrolysis of nitriles with dilute acid or dilute alkali followed by acidification (c) hydrolysis of esters with dilute acid or dilute alkali and heat followed by acidification
- describe: (a) the redox reaction with reactive metals to produce a salt and H2(g) (b) the neutralisation reaction with alkalis to produce a salt and H2O(l ) (c) the acid–base reaction with carbonates to produce a salt and H2O(l) and CO2(g) (d) esterification with alcohols with concentrated H2SO4 as catalyst (e) reduction by LiAlH4 to form 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.
Tips to avoid common mistakes in Carboxylic acids
- › Check the question conditions carefully; use 22.4 dm³ per mole for calculations involving gas at s.t.p.
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) → 2RCOOM(aq) + H₂(g), where M is a reactive metal like magnesium or zinc. A salt and hydrogen gas are formed.
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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