Question

An aqueous solution ‘A’ turns phenolphthalein solution pink. When another aqueous solution ‘B’ is added to the pink solution, the pink color disappears. Adding a few drops of solution ‘A’ again restores the pink color. The respective changes in the nature of the solution are:

• A. basic → acidic → basic
• B. acidic → basic → acidic
• C. basic → basic → acidic
• D. basic → acidic → basic

Answer 1

The Correct Option is D

Step 1: Understand the behaviour of phenolphthalein
Phenolphthalein is a pH indicator used to detect acids and bases:
- It turns pink in basic solutions.
- It remains colorless in acidic solutions.

Step 2: Analyze what happens in the question
- Solution ‘A’ turns phenolphthalein pink → So, ‘A’ is basic.
- Adding solution ‘B’ causes the pink color to disappear → So, ‘B’ is acidic, as it neutralizes the base.
- Adding more of solution ‘A’ brings back the pink color → The solution becomes basic again.

Step 3: Conclusion
The nature of the solution changes in the following sequence:
Basic → Acidic → Basic

Final Answer:
basic → acidic → basic