i want to know the definition of compressibility factor ,how is it helpful in explaining the deviation of real gases from ideal behavior .Plot a graph between compressibility factor for some of the real gases at 273k

Dear student
Compressibility factor (Z):It is the measure of deviation from ideal behavior.

According to ideal gas equation PV=nRTAn ideal gas obeys this equation through all P & T ranges.
However real gases do not always obey this gas law. Hence a factor called as compressibility factor Z is introduced
When, PV=nRT Then Z is assumed to be 1

Compressibility factor,

In case of a real gas Z may be greater or smaller than 1

If Z>1 the gas more compressible and shows a negative deviation from ideal gas behaviour,

If Z<1 Then gas is less compressible and shows positive deviation from ideal gas behaviour. 

The graph is as shown below:

Regards