WAEC Chemistry 2021 Theory — Question 16
Question 16 of 31 from the West African Examinations Council (WAEC) Chemistry 2021 Theory paper, with the correct answer and a full explanation.
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3(a). (i) What are acid-base indicators? (ii) Name a suitable indicator for titrating a weak acid against a strong base. (iii) Give a reason for your answer in (ii).
Model answer
(i) Acid-base indicators are dyes that change colour depending on the acidity/alkalinity (pH) of the solution. (ii) Phenolphthalein. (iii) The reaction between a weak acid and a strong base has a slightly alkaline end-point, so an indicator that changes colour in the alkaline range (phenolphthalein) is required.
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