Question

For the ideal gas law to be most applicable, it is best for the gas to exist at?

Answer 1

The ideal gas equation is given by PV=nRT

where, P= Pressure of gas; V= Volume of gas; n= no of moles; R is universal gas constant and T is temperature.

The ideal gas equation is most applicable under the conditions of High temperature and Low pressure. This can be understood by Kinetic theory of gases. Ideal gas equation is based on kinetic theory of gases. Two important postulates of this theory are :-

1. The volume occupied by gas molecule is negligible in comparision to the volume of container.

2. The intermolecular forces between gas molecules are negligible.

So, for a gas to behave as ideal, the above two postulates must be followed.

To make the volume of gas molecules negligible in comparision to container, we have to increase the size of container. This is because the size of gas molecules is fixed and can't be changed. By increasing the container volume, what is implied is that the gas should occupy a large volume. This can be done by reducing the pressure. This is because according to Boyle's law, the volume of a gas is inversely proportional to pressure at constant temperature. So, in order to increase the volume occupied, pressure must be reduced.

For the second assumption to be true, the gas molecules should be moving at high speeds. This is becuase if they move slowly, they will be in close proximity to each other for a longer period of time and the chances of interacting with each other will be high. Thus, the intermolecular forces will not be negligible. One thing to minimize this intermolecular interaction is to increase the temperature. This is because on increasing temperature, the kinetic energy of gas molecules increases and they start to move at high speeds. At high speed, the gas molecules don't have sufficient time to interact as they are in constant motion and are not in contact for sufficient time to interact with each other.