Which of the following changes occurs when phenolphthalein is added in acidic and basic solutions respectively:

see full answer

Talk to JEE/NEET 2025 Toppers - Learn What Actually Works!

Real Strategies. Real People. Real Success Stories - Just 1 call away

An Intiative by Sri Chaitanya

Colourless and pink

Colourless and blue

Pink and colourless

Blue and colourless

answer is A.

(Unlock A.I Detailed Solution for FREE)

Ready to Test Your Skills?

Check your Performance Today with our Free Mock Test used by Toppers!

Take Free Test

Detailed Solution

Concept- Since phenolphthalein may change colour at various pH levels, it serves as an example of an acid-base indicator. Phenolphthalein is colourless from pH levels below 7 to 8.2, when it starts to turn pink, and to pH levels above 10, when it turns magenta.

The weak basic phenolphthalein is colourless in an acidic solution and becomes pink in an alkaline solution. When the solution is acidic, the equilibrium in the above reaction is to the left, and the concentration of the anions is too low to be able to see the pink colour.
When the solution is basic, however, the equilibrium is to the right and the concentration of the anion is high enough to see the pink colour.
Hence, the correct answer is option 1.

Watch 3-min video & get full concept clarity

Result Producing online coaching for JEE/NEET of south India

Largest All India Test Series for JEE/NEET

Best Online Course for IIT JEE

Best Online Course for NEET

Best Online Course for CBSE