Question

An aqueous solution ‘A’ turns phenolphthalein solution pink. In addition of an aqueous solution ‘B’ to ‘A’, the pink color disappears. The following statement is true for solution ‘A’ and ‘B’.

• A. A is strongly basic and B is a weak base.
• B. A is strongly acidic and B is a weak acid.
• C. A has pH greater than 7 and B has pH less than 7.
• D. A has pH less than 7 and B has pH greater than 7.

Answer 1

The correct option is C

A has pH greater than 7 and B has pH less than 7.

Explanation for correct option

(C)A has pH greater than 7 and B has pH less than 7.

• Phenolphthalein solution behaves as an acid-base indicator.
• Phenolphthalein solution changes to pink when a basic substance is added to it.
• Phenolphthalein solution does not indicate the strength of acids or bases.
• As soon as acid is added to it, the pink color disappears.
• So, A is base, and B is acid.
• Therefore, A has pH greater than 7 and B has pH less than 7.

Explanation for incorrect option

A has pH greater than 7 and B has pH less than 7. Hence, options (A), (B), (D) are incorrect.

Hence, option (C) is correct. A has pH greater than 7 and B has pH less than 7.