In thermodynamics, the $P-V$ work done is given by $$ w=-\int d V P_{e x t} $$ For a system undergoi

Question

In thermodynamics, the $P-V$ work done is given by $$ w=-\int d V P_{e x t} $$ For a system undergoing a particular process, the work done is,\ $w=-\int d V\left(\frac{R T}{V-b}-\frac{a}{V^{2}}ight)$\ This equation is applicable to a\

Professor PC Thomas Classes · Answer

( $\mathrm{a}, \mathrm{b}, \mathrm{c}$ ) : The following expression of $P-V$ work done\ $w=-\int P_{e x t} d V$\ is applicable for reversible isobaric as well as isothermal and adiabatic processes. If $P_{	ext {ext }}$ is substituted for a van der Waals equation then it becomes $$ w=-\int\left(\frac{R T}{V-b}-\frac{a}{V^{2}}ight) d V $$ But it is not applicable for irreversible processes which are carried out very fast. So, work done is calculated assuming final pressure remains constant throughout the process.\