Question

An ideal gas is allowed to expand against a constant pressure of 2 bar from 10L to 50 L in one step. 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 ?
(Give that, 1 L bar = 100 J)

Answer 1

In the first case, as the expansion is against constant external pressure
`W = p_("ext") (V_(2) - V_(1)) = - 2 "bar" xx (50 - 10) L`
`= - 80 L "bar" " " (1 L "bar" = 100 J)`
`= - 80 xx 100 J`
`= - 8 kJ`
If the given expansion was carried out reversibly, the internal pressure of the gas should be greater than the external pressure at every stage. Hence, the work done will be more