When a student added universal indicator solution to one of the following chemicals, its colour changed to navy blue. The chemical is most likely to be :
(1) lemon juice (2) milk of magnesia
(3)vinegar (4)tomato juice
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Correct answer: (2) milk of magnesia

Explanation: Universal indicator is used to check the pH of unknown solutions. Bases turn universal indicator to blue. As milk of magnesia is a base, so it will turn the universal indicator blue.