9. Assertion : At critical temperature, surface tension of a liquid becomes zero. Reason : At this temperature, intermolecular forces for liquids and gases become equal. Liquid can expand without any restriction.

Read the assertion and reason carefully to mark the correct option out of the options given below:

(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 the assertion and reason both are false.

(e)       If assertion is false but reason is true.

Ans. (a) Zero surface tension means no opposition to expansion.

(11)