In thermodynamics the P-V work done is given by

$\mathrm{w}=-\int {\mathrm{dVP}}_{\mathrm{ext}}.$

For a system undergoing a particular process, the work done is , 

$\mathrm{W}=-\int \mathrm{dV}\left(\frac{\mathrm{RT}}{\mathrm{V}-\mathrm{b}}-\frac{\mathrm{a}}{{\mathrm{V}}^2}\right)$

This equation is applicable to a 

Process that is irreversible and at constant isothermal. 

Process that is reversible and isothermal.

Process that is reversible and adiabatic.

System that satisfies the van der Waals equation of state.