Question

In which solution will thymol blue indicator appear blue?

Answer 1

In 0.1 M KOH, thymol blue indicator would appear blue. 

Answer 2

Answer: (2) 0.1 M KOH

Explanation:

Thymol blue is an universal indicator. Thymol blue has a blue color when in basic conditions (pH > 7), a green color in neutral conditions (pH =7), and a yellow color in acidic conditions (pH < 7).

pH or pOH is the measure of acidity or alkalinity of a solution.  pH is calculated by taking negative logarithm of hydrogen ion concentration.

0.1 M $CH_3COOH$ ,  0.1 M $HCl$  and  0.1 M $H_2SO4$ are all acidic in nature.

Thus thymol blue will appear blue in basic 0.1 M KOH.