Adding an inert gas at constant volume to a gaseous equilibrium:

1. At constant volume, partial pressures of the reacting species do not change when an inert gas is added. 2. Total pressure rises, but P_A, P_B etc are unchanged. 3. Reaction quotient Q = K_p still — no shift. 4. At constant PRESSURE (not volume), inert gas addition decreases reactant partial pressures and CAN shift equilibrium. _Source: NCERT Class 11 Chem Ch 7 §7.6 Effect of Inert Gas_