introducing new gas to increase pressure

[Andrew Sun 3F]

I know that Dr. Lavelle said that introducing new gases doesn't shift equilibrium. However, how come it doesn't cause the reaction to shift towards the side with less moles? I think conceptually I am unsure.

[Emaad Sohail 3F]

While I'm not entirely sure myself, I think it's because adding another gas doesn't affect the concentration if the volume is kept constant- you still have the same number of moles in the same space, so the concentration stays the same. This means the K equation doesn't change since the concentrations are still the same.

[Molly McAndrew 1 1H]

Increasing pressure can change the concentration of reactants or products and cause the reaction to shift one way or the other. However, the reaction will return to equilibrium following this shift and the equilibrium constant (i.e. ratio of products/reactants) will remain the same. Dr. Lavelle emphasizes that while the concentration of gases can change and likely will, a change in pressure will not change the equilibrium constant.