Question

There is more deviation in the behaviour of a real gas from ideal gas equation PV = nRT

• A. at high temperature and low pressure
• B. at low temperature and high pressure
• C. at high temperature and high pressure
• D. at low temperature and low pressure

Answer 1

The correct option is A at high temperature and low pressure

Gases are expected to behave ideally and follow the equation $PV=nRT$.

But, the significant deviation from ideal behavior is observed at high temperature and low pressure. Because the molecules of an ideal gas are assumed to have zero volume, the volume available to them for motion is always the same as the volume of the container. In contrast, the molecules of a real gas have small but measurable volumes. At low pressures, the gaseous molecules are relatively far apart, but as the pressure of the gas increases, the inter-molecular distances become smaller and smaller.

As a result, the volume occupied by the molecules becomes significant compared with the volume of the container. Consequently, the total volume occupied by the gas is greater than the volume predicted by the ideal gas law. Thus at very high pressures, the experimentally measured value of $PV=nRT$ is greater than the value predicted by the ideal gas law