Q.

A gas is compressed isothermally to half its initial volume. The same gas is compressed separately through an adiabatic process until its volume is again reduced to half. Then   [2016]

1 Compressing the gas isothermally or adiabatically will require the same amount of work.  
2 Which of the case (whether compression through isothermal or through adiabatic process) requires more work will depend upon the atomicity of the gas.  
3 Compressing the gas isothermally will require more work to be done.  
4 Compressing the gas through adiabatic process will require more work to be done.  

Ans.

(4)

V1=V, V2=V/2

On P–V diagram, Area under adiabatic curve > Area under isothermal curve.
So, compressing the gas through adiabatic process will require more work to be done.