No work is done by the system, when a reaction occurs at constant

Solution (By Examveda Team)

Here work means expansion work since the expansion work ($$W$$) and we know expansion work $$W = \int {} {P_{ext}}dV$$   and since for isochoric process there will be no volume change i..e.., volume remains constant and hence $$dV = 0.$$
So, work done $$= 0$$