Work done in chemical reaction

The work done by a system at constant temperature and pressure is $W = -P_{ext}\,\Delta V$. Assuming $P_{ext} = P$,

If the gases were ideal, using Eq. (4.26), $PV_1 = n_1RT$ and $PV_2 = n_2RT$. At constant temperature and pressure,

The above equation gives the work done by the system in chemical reactions. The sign of $W$ depends on $\Delta V$. We consider the following cases:

i. If $n_2 > n_1$, $\Delta n_g$ is positive and $W < 0$, or work is done by the system.

ii. If $n_1 > n_2$, $\Delta n_g$ is negative and $W > 0$, or work is done on the system. …