Question

Statement - I
A cylinder fitted with a movable piston contains a certain amount of liquid in equilibrium with its vapor. The temperature of the system is kept constant. If the volume of the vapor is decreased by moving the piston inwards, the vapor pressure will remain unchanged.
Statement - II
Vapor, in equilibrium with its liquid, at constant temperature does not obey Boyle's law.

• A. Statement - I is true, Statement - II is true; statement - II is a correct explanation for Statement - I.
• B. Statement - I is true, Statement - II is true; statement - II is NOT a correct explanation for Statement - I.
• C. Statement - I is true, Statement - II is false.
• D. Statement - I is false, Statement - II is true.

Answer 1

The correct option is A Statement - I is true, Statement - II is true; statement - II is a correct explanation for Statement - I.

In statement $-II,$ Equilibrium means when rate of condensation becomes equal to rate of evaporation. At this state equilibrium is said to be established.

Therefore, the vapors are saturated vapors and these saturated vapors do not obey Boyle's law because saturated vapor pressure is the maximum pressure and when volume, is decreases at saturated, the vapor condense to maintain the same pressure.

As Boyle's law is $P\propto \frac{1}{v}$ at constant $T$ where $P$ is pressure and $V$ is volume and $T$ is temperature.

So, as in statement$-I$, by decreasing volume, our pressure remains unchanged that's why it do not follow Boyle's law.

Hence, the answer is statement$-I$ is true,statement $-II$ is true; statement $-II$ is a correct explanation for statement$-I.$