Carboxylic acids Cambridge IGCSE Chemistry revision
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In plain words
Vinegar is a dilute solution of ethanoic acid, which is what you get when the ethanol in wine is left open to the air. Carboxylic acids like it are weak acids: they do everything an acid does, just more gently than hydrochloric acid.
Three things to know
- Ethanoic acid, CH₃COOH, is a weak acid. It reacts with metals, bases and carbonates to make salts called ethanoates.
- It is made by oxidising ethanol: with an oxidising agent, or slowly by bacteria in the air, which is how wine turns to vinegar.
- A carboxylic acid reacts with an alcohol, with an acid catalyst, to make an ester and water.
Tips and tricks
- Carboxylic acids are still acids: they fizz with carbonates and with reactive metals. The salts are ethanoates.
- "Weak" means only partly ionised. It does not mean dilute.
It lands in your notebook with its questions as flashcards.
Carboxylic acids: 6 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
What is the functional group of the carboxylic acids?
It is the group that releases H⁺.
In which everyday liquid is ethanoic acid found?
Vinegar is a dilute solution of ethanoic acid.
Which gas is given off when ethanoic acid reacts with magnesium?
Acid + metal → salt + hydrogen.
What is made when a carboxylic acid reacts with an alcohol?
Water is the other product.
What is the pH of dilute ethanoic acid most likely to be?
It is a weak acid, so it is acidic but not strongly so.
What type of reaction changes ethanol into ethanoic acid?
The ethanol gains oxygen.
Quiz
6 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
4 questions, 7 marks. Write your answers on paper, then check them.
Carboxylic acids
Cambridge IGCSE Chemistry 0620 · 7 marks · papermunch.org
Name ______________________________ Date ______________
Name the three products formed when ethanoic acid reacts with sodium carbonate.[2]
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Sodium ethanoate, water and carbon dioxide.
Describe two ways in which ethanol can be changed into ethanoic acid.[2]
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By heating it with an oxidising agent, and by leaving it open to the air, where bacteria oxidise it.
Explain why ethanoic acid is described as a weak acid.[1]
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It is only partly ionised (dissociated) in water.
Name the two kinds of compound that react together to make an ester, and the other product.[2]
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A carboxylic acid and an alcohol. Water.
Answers: Carboxylic acids
- 1. Sodium ethanoate, water and carbon dioxide.
- 2. By heating it with an oxidising agent, and by leaving it open to the air, where bacteria oxidise it.
- 3. It is only partly ionised (dissociated) in water.
- 4. A carboxylic acid and an alcohol. Water.