Question

An ideal gas is heated in a container that has a fixed volume. Identify which of the following will increase as a result of this heating?
I. The pressure against the walls of the container
II. The average kinetic energy of the gas molecules
III. The number of moles of gas in the container

• A. I only
• B. I and II only
• C. II and III only
• D. II only
• E. III only

Answer 1

The correct option is B I and II only

Ideal gas equation : $PV=nRT$ $⟹P=\frac{nRT}{V}$

Number of moles of gas (n) remains constant because the volume of gas is constant.

As the container has fixed volume i.e $V=constant$ $⟹P\propto T$ .........(1)

Due to heating, the temperature of the gas increases.

Equation (1) implies that the pressure-exerting against the wall by gas molecules also increases.

Average kinetic energy of molecules $K.E=\frac{3}{2}{k}_{B}T$ $⟹$ $K.E\propto T$

Thus average kinetic of the gas molecules increases with the increase in temperature.

Hence option B is correct.