Q.What is the effect of added inert gas on the reaction at equilibrium?

Le Chatelier's Principle

Le Chatelier's principle states that when a system at equilibrium is disturbed by a change in concentration, pressure or temperature, the equilibrium shifts in the direction that partially opposes the change.

• Concentration: adding a reactant (or removing a product) shifts the equilibrium forward.
• Pressure: increasing pressure shifts the equilibrium towards the side with fewer gaseous moles. For $\mathrm{A(g) + \tfrac{1}{2}B(g) \rightleftharpoons C(g)}$ the forward side has fewer moles, so high pressure favours products.
• Temperature: for an exothermic reaction (heat is a product, e.g. $\mathrm{N_2 + 3H_2 \rightleftharpoons 2NH_3 + heat}$) raising the temperature shifts equilibrium backward and lowers the yield, while for an endothermic process (e.g. dissolution of many salts) a rise in temperature shifts it forward, increasing solubility.
• Catalyst: speeds up both directions equally and does not change the equilibrium position. …