Question

An ideal gas is allowed to expand against a constant pressure of 2 bar from 10 L to 50 L in one stop. Calculate the amount of work done by the gas. If the same expansion were carried out reversibly,will the work done be higher or lower than the earlier case ?

Answer 1

In the first case, as the expansion is against constant external pressure, ,brgt `w= - P_(ext) (V_(2)-V_(1)0 = - 2 "bar" xx ( 50-10) L= -80 L "bar" = - 80 xx 100 J = - 8 kJ ( 1L `bar` = 100 J) `
If the above expansion were carried out reverisbly, the internal pressure of the gas should be infinitesimally greater than the external pressure at every stage. Hence, the work done will be more.