DIFFERENCES BETWEEN REAL GAS AND IDEAL GAS

A gas which obeys the ideal gas equation, PV = nRT under all conditions of temperature and pressure is called an ideal gas. There is no gas which obeys the ideal gas equation under all conditions of temperature and pressure. The gases are found to obey the gas laws if the pressure is low or the temperature is high. Such gases are known as real gas. Some other differences between real and ideal gas are shown in tabular form below;

PV = znRT    Where ‘z’ is correction factor known as compressibility factor.

z = PV/nRT

For ideal gas, z=1 and for real gas z=1

1. At low temperature and low pressure, ‘z’ is less than one that means real gas is more compressible than ideal gas.
2. At high temperature and high pressure, ’z’ is more than one that means real gas is less compressible than ideal gas.
3. At high temperature and low pressure, ‘z’ is equal to 1 i.e. Real gas behaves as ideal gas.

The extent of deviation of real gas from ideal behavior depends on temperature and pressure. The effect of pressure on the deviation of real gas from ideal behavior can be understood by plotting graph i.e. PV against P at room temperature( constant temperature) by taking different gases like H₂, N₂, He, etc

Similarly,the effect of temperature on the deviation of real gas from ideal behavior can be understood by plotting PV against P in graph at different temperature by taking nitrogen gas. Real gas behaves ideally as temperature increases.

Similarly, a term ‘an²/v²’ is added to observe pressure which provides molecular attraction where, ‘a’ is Vander Waal's constant (Pressure correction) whose value depends on the nature of gas.