In which of the following equilibrium, change in volume of the system does not alter the number of mole?
For the reaction,
N2(g)+O2(g)⇌2NO(g)
Δng=0
As there is an equal number of moles on both sides of the reaction, an increase in volume will have no effect on the equilibrium and thus there is no shift in the direction. Similarly, on decreasing the volume there is no effect on the equilibrium.
Hence, option A is correct.