Question

An ideal gas, obeying kinetic theory of gases cannot be liquefied, because:
a.) It solidifies before becoming a liquid
b.) Forces acting between its molecules are negligible
c.) Its critical temperature is above ${{0}^{o}}C$
d.) Its molecules are relatively small in size.

Answer 1

Hint: An ideal gas is defined as that there are no intermolecular forces between them. Such a type of system can only exist as a gas. Any real system will show ideal gas behaviour when the pressure is extremely low and the temperature is high to overcome the attractive intermolecular forces.

Complete answer:
In the question it is given that an ideal gas obeys kinetic theory of gases.
According to the kinetic theory of gases, the gas molecules are very small compared to the distance between molecules. The gas molecules are in constant and random motion and frequently collide with each other and collide with the walls of the container. At higher temperatures, the greater the motion of the gas molecules.
Coming to given options, option A, It solidifies before becoming a liquid, it is wrong because we cannot solidify an ideal gas.
Coming to option C, Its critical temperature is above ${{0}^{o}}C$, there is no role for critical temperature because ideal gases cannot be liquefied. So, this option is not correct.
Coming to option D, Its molecules are relatively small in size. There is no relation between the size of the gas molecules and its liquefaction for ideal gas. So, this option is not correct
Coming to option B, Forces acting between its molecules are negligible. This option is correct because Forces acting between its molecules are negligible for ideal gas. There should be an intermolecular force of attraction between the molecules of the ideal gas to become liquid. Without the force of attraction, it's not possible to liquify any gas.
So, the correct answer is “Option B”.

Note: We know that ideal gas has no force of attraction between them and occupies negligible volume. If any gas won’t have any force of attraction between then we cannot liquefy that gas at any temperature and pressure. But in case of real gases, there is a force of attraction between their molecules and when the force of attraction is increased, they can be liquified.