Which of the following is an acid-base indicator?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Turmeric
An indicator is a substance that shows by a change of colour whether a solution is acidic or basic. Turmeric is a natural indicator: it stays yellow in acids and neutral solutions and turns red in bases.
Why the other options are incorrect
Option (1) Vinegar — Incorrect. Vinegar is an acid (it contains acetic acid), not an indicator.
Option (2) Lime water — Incorrect. Lime water is a solution of calcium hydroxide, a base.
Option (4) Baking soda — Incorrect. Baking soda is sodium hydrogencarbonate, a basic salt.