When a student added red litmus to an aqueous solution, the red litmus turned blue. Which one of the following should be added in excess so that the change in colour is reversed?
(1) baking soda solution
(2) lime water
(3) vinegar solution
(4) ammonia solution

Correct answer: (3) vinegar solution

Explanation: Acids turn blue litmus red and bases turn red litmus blue. When the student added red litmus to the aqueous solution, it turned blue i.e the solution is basic. In order to reverse the change in colour, now he has to add an acid to the solution in excess. As in the given options, vinegar solution is acidic as it is made of ethanoic acid. Hence, the correct answer is vinegar solution.

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Updated on: 10-Oct-2022

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