Titration
3 marks · NormalExplain why phenolphthalein is a better choice of indicator for an acid–alkali titration than universal indicator. Include two reasons in your answer.
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Also accept: methyl orange (if justified)
Common mistakes: saying universal indicator 'does not work' without explanation
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Marking points
B1 · 1 mark · Identifies that phenolphthalein gives a sharp/clear colour change at endpoint.
B2 · 1 mark · States that universal indicator gives a range of colours or changes gradually.
B3 · 1 mark · Links the sharp endpoint/unclear endpoint to precise or accurate titration.
Worked solution
Phenolphthalein is better because it changes colour sharply (from colourless to pale pink) at the endpoint, making it easy to see. Universal indicator changes gradually through several colours, making it hard to spot a clear endpoint. A definite colour change gives a more accurate titration result.