7.9 Carboxylic acids and esters
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What is the functional group of a carboxylic acid?
Choose one answer.
Correct Not quite: the answer is –COOH
Mark scheme
D
Model answer
D: carboxylic acids contain –COOH.
Name the carboxylic acid with the formula C2H5COOH.
Mark scheme
- propanoic acid (1)
Model answer
Propanoic acid (it has 3 carbon atoms).
Ethanoic acid is added to sodium carbonate.
Describe what you would see and name the gas produced.
Mark scheme
- fizzing / bubbles (1)
- carbon dioxide (1)
Model answer
It fizzes, giving off carbon dioxide gas.
Explain why ethanoic acid is described as a weak acid.
Mark scheme
- it only partially ionises in water (1)
- so it releases fewer \mathrm{H^+} ions (than a strong acid of the same concentration) (1)
Model answer
Only a small fraction of ethanoic acid molecules ionise in water to release hydrogen ions, so it is a weak acid.
Name the ester made from ethanol and ethanoic acid, and give one use of esters.
Mark scheme
- ethyl ethanoate (1)
- perfumes / flavourings / solvents (1)
Model answer
Ethyl ethanoate; esters are used in perfumes and food flavourings.
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