Question

Assertion: Phenolphthalein gives pink colour in basic solution. Reason: Phenolphthalein is a natural indicator.

a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion. b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion. c) The Assertion is true but the Reason is false. d) The statement of the Assertion is false but the Reason is true.

Answer 1

Answer: (c) assertion is true but reason is false

Explanation:

Phenolphthalein is often used as an indicator in acid-base titrations. It will appear pink in basic solutions and clear in acidic solutions. ... Hence, phenolphthalein is chosen because it changes colour in a pH range between 8.3 – 10.

Answer 2

For the given assertion and reason the correct option is:

(c) The Assertion is true but the Reason is false.

Justification for the answer:

ASSERTION IS TRUE AS:-

• Phenolphthalein is a color indicator for different chemical compounds.
• Through its change of color, it indicates whether the compound or solution is basic or acidic.
• It remains colorless in acidic solutions indicating the acidic level.
• And, changes its color to pink when tested for a basic solution indicating its basic nature.

REASON IS FALSE AS:-

• Phenolphthalein(C20H14O4) is not a natural indicator.
• It is an organic compound used as an acid-base indicator.
• It is generally used in laboratories for testing the solutions' acidity, that is whether the solution is an acid or a base.
• Natural indicators are those which occur naturally such as onions, beetroots, turmeric, etc.