Question

On adding phenolphthalein indicator to a colorless solution, no change is observed. What is the nature of this solution?

• A. Basic
• B. Either acidic or basic
• C. Either acidic or neutral
• D. Either basic or neutral

Answer 1

The correct option is C

Either acidic or neutral

The correct option is (C):

Explanation for the correct answer:

Either acidic or neutral

1. Phenolphthalein is actually slightly soluble in water and for the experiments it is dissolved in the alcohols.
2. One popular application of the phenolphthalein is as an indicator in the acid-base titrations.
3. It is a weak acid and in the solutions it will lose the ${\mathrm{H}}^{+}$ ions.
4. The molecules of the phenolphthalein is colorless, and the ion of phenolphthalein is purple.
5. So, basically the color of phenolphthalein indicator will not change with and acidic or the neutral solution.

Explanation for the incorrect answers:

Option (A):

Basic:

1. Phenolphthalein is slightly soluble in water and is used in acid-base titrations.
2. On adding it to the basic solution, the color will change to pink.
3. Therefore, change is observed in this case.
4. Hence, this is an incorrect option.

Option (B):

Either acidic or basic

1. Phenolphthalein is slightly soluble in water and is used in acid-base titrations.
2. On adding it to the basic solution, the color will change to pink so the change is observed in this case.
3. But on adding phenolphthalein to acidic solution, no change is observed.
4. Hence, this is an incorrect option.

Option (D):

Either basic or neutral

1. Phenolphthalein is slightly soluble in water and is used in acid-base titrations.
2. On adding it to the basic solution, the color will change to pink so the change is observed in this case.
3. But on adding phenolphthalein to a neutral solution, there won't be any change.
4. Hence, this is an incorrect option.

Hence, The correct option is (C): Either acidic or neutral