An aqueous solution ‘A’ turns phenolphthalein solution pink. On addition to an aqueous solution ‘B’ to ‘A’, the pink colour 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.
Ans.
Phenolphthalein is an indicator which is
- colorless in acidic solutions
- And, turns dark pink in basic solutions.
Since
- A turns the color of solution to dark pink, it is basic in nature and has a pH more than 7.
- On the other hand, when B is added to A, the pink color disappears. Therefore, B is acidic in nature and has a pH below 7
So, the correct option is
(c)
