Question

At critical temperature, surface tension of a liquid is:

• A. zero
• B. infinite
• C. varies liquid to liquid
• D. cannot be measured

Answer 1

Answer: (A)

zero

The relation between surface tension and critical temperature.

$\Rightarrow \sigma V_M^{2/3}=k(T_C-T-6)$
where $\sigma =\text{Surface tension},V_M=\text{Molar volume},k=\text{Propotional factor for non- polar liquid}=2.2\times {10}^{-7}J{K}^{-1}$
At $T=T_C\Rightarrow \sigma \approx 0$
The surface tension of a liquid decreases with increases of temperature and becomes zero at its critical temperature.

Hence, the correct answer is option $\text{A}$.