In a reversible chemical reaction (where, Δx = number of moles of products-number of moles of reactants )

• addition of inert gas favours the forward reaction, when Δx is positive.
• pressure has no effect on equilibrium, when Δn = 0.
• addition of inert gas has no effect on the equilibrium constant at constant volume for any value of Δx (+ ve, - ve) or zero).
• all 'a', 'b' & 'c'.