Reaction with metals
3 marks · EasyEthanoic acid is a weak acid. A student places blue litmus paper into a solution of ethanoic acid and measures the pH.
State the expected colour change of the litmus paper.
Ethanoic acid reacts with sodium carbonate solution. Write the chemical name of the gas produced.
Describe what is meant by a 'weak acid' in terms of ionisation in water.
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(a) Blue to red
(b) Carbon dioxide
(c) Only partially ionises in water · must show partially ionises, does not fully ionise
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Marking points
B1 (a) · 1 mark · Correct colour change stated: from blue to red.
B2 (b) · 1 mark · Gas named as carbon dioxide.
B3 (c) · 1 mark · States 'partially ionises in water' or equivalent.
Worked solution
a) The blue litmus paper turns red because ethanoic acid is acidic.
b) Ethanoic acid reacts with sodium carbonate to produce carbon dioxide gas.
c) A weak acid only partially ionises in water, so only some of its molecules release H+ ions.