Question

Correct combination among the following is
i) Water can be converted into vapour at ${100}^{0}C$ only
ii) Vapour pressure can be increased more than the atmospheric pressure at a certain temperature.
iii) Lowering of vapour pressure is directly proportional to mole fraction of solute.

• A. All are correct
• B. ii only wrong
• C. iii only correct
• D. All are wrong

Answer 1

Answer: (C)

iii only correct

Using clausius clapeyron equation,
we get $log\frac{P_2}{P_1}=-\frac{\Delta H}{R}\times (\frac{1}{T_1}-\frac{1}{T_2})$
Therefore, at any particluar temperature, the vapour pressure of solution is unique.
Also, conversion to vapour of a liquid can take place at many temperatures and many pressure values.
The third statement is the outcome of Raoult's law.