Question

Which of the following is not an assumption of the kinetic theory of gases?
a-Collisions of gas particles are perfectly elastic.
b-Gas particles have negligible volume.
c-At high pressure, gas particles are difficult to compress.
d-A gas consists of many identical particles which are in continual motion.

Answer 1

. Kinetic theory of gases explains the movement of gas particles in a closed system. It postulates about the velocities, collisions, and their motion. The effect of pressure is not explained in it.

Complete step by step answer:
The assumptions of the kinetic theory of gases are:
-The gases are composed of a huge number of identical molecules, spherical atoms or molecules, which are moving in random directions. They are separated by distances that are very large in comparison with their size. This leads to the negligible volume of the particle itself in comparison to the whole.
-The kinetic energy is transferred between molecules by heat energy and they are always in random motion, which is called Brownian motion.
- The molecules undergo perfectly elastic collisions with each other and with the walls of the container, in which no energy loss occurs at all. They do not interact in general .i.e. there is no intermolecular force between gas molecules.
This model describes a perfect gas and it is a valid approximation for a real gas. This theory is particularly applicable in case of extreme dilution and high temperature. Real gases behave like ideal gas; they should be treated under high temperature and low pressure.
So, the correct answer is “Option C”.

Note: When pressure is applied to the gas, molecules come closer to each other. In this situation, intermolecular forces become active and the volume of the gas particles are no more negligible in comparison to the whole. As a result, gas is no more ideal then.