How does a carboxylic acid react with a carbonate?

It liberates carbon dioxide (effervescence), forming a salt and water.

Why are carboxylic acids classed as weak acids?

They only partly dissociate in water.

What are the reagents and catalyst for making an ester?

A carboxylic acid and an alcohol, with an acid catalyst (concentrated sulfuric acid).

Write the equation for ethanoic acid with ethanol.

CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ + H₂O

Give three uses of esters.

Solvents, plasticisers, perfumes and food flavourings (any three).

What are vegetable oils and animal fats esters of?

Propane-1,2,3-triol (glycerol) with long-chain carboxylic acids.

What forms when an ester is hydrolysed by acid?

A carboxylic acid and an alcohol (reversible).

What forms when an ester is hydrolysed by aqueous NaOH?

The sodium salt of the carboxylic acid and an alcohol.

The sodium salt of a long-chain carboxylic acid, made by alkaline hydrolysis of fats and oils.

What is biodiesel and how is it made?

A mixture of methyl esters of long-chain carboxylic acids, made from vegetable oil and methanol with a catalyst.

Carboxylic acids and estersAQA A-Level Chemistry: Flashcards

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What is the functional group of a carboxylic acid?

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What is the functional group of a carboxylic acid?: –COOH, the carboxyl group.
What is the general formula of an ester?: RCOOR′.
How does a carboxylic acid react with a carbonate?: It liberates carbon dioxide (effervescence), forming a salt and water.
Why are carboxylic acids classed as weak acids?: They only partly dissociate in water.
What are the reagents and catalyst for making an ester?: A carboxylic acid and an alcohol, with an acid catalyst (concentrated sulfuric acid).
Write the equation for ethanoic acid with ethanol.: CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ + H₂O
Give three uses of esters.: Solvents, plasticisers, perfumes and food flavourings (any three).
What are vegetable oils and animal fats esters of?: Propane-1,2,3-triol (glycerol) with long-chain carboxylic acids.
What forms when an ester is hydrolysed by acid?: A carboxylic acid and an alcohol (reversible).
What forms when an ester is hydrolysed by aqueous NaOH?: The sodium salt of the carboxylic acid and an alcohol.
What is soap?: The sodium salt of a long-chain carboxylic acid, made by alkaline hydrolysis of fats and oils.
What is biodiesel and how is it made?: A mixture of methyl esters of long-chain carboxylic acids, made from vegetable oil and methanol with a catalyst.

Exam questions on Carboxylic acids and esters

A student adds a sample of ethanoic acid to aqueous sodium carbonate. In a separate experiment she warms ethanoic acid with ethanol and a few drops of concentrated sulfuric acid.
Write the equation for the reaction of ethanoic acid with sodium carbonate.2 marks
Methyl butanoate has a fruity smell like apples and is used in food flavourings and perfumes. It is made in the laboratory from a carboxylic acid and an alcohol.
Write the equation for the formation of methyl butanoate and name a suitable catalyst.2 marks
A company manufactures soap and biodiesel from vegetable oil. Vegetable oils and animal fats are esters of propane-1,2,3-triol with long-chain carboxylic acids.
Describe what happens when a vegetable oil is heated with aqueous sodium hydroxide, naming the products.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).