Assertion : The impurities always decrease the surface tension of a liquid.
Reason : The change in surface tension of the liquid depends upon the degree of contamination of the impurity.

Options

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false.
D. If assertion is false but reason is true.

Answer

D

Explanation

The presence of impurities either on the liquid surface or dissolved in it, considerably affect the force of surface tension, depending upon the degree of contamination. A highly soluble substance like sodium chloride when dissolved in water increase the surface tension. But the sparingly soluble or substance like phenol when dissolved in water reduces the surface tension of water.