Inert Gases and Equilibrium Constant

[Areena H 2K]

Why does removing or adding an inert gas in a chemical equation not change the equilibrium constant?
Adding or removing an inert gas affects the pressure and physical parameters based on La Chatalier's Principle since physical parameters cause a shift in the reaction, so why do we say that inert gases don't cause a shift?

[Alice Chang 2H]

I thought this site helped a bit to explain: https://chemistry.stackexchange.com/questions/18567/what-would-be-the-effect-of-the-addition-of-an-inert-gas-to-a-reaction-at-equili

Basically, inert gasses only affect equilibrium if the volume changes.

[Hussain Chharawalla 1G]

I believe that's the point Dr. Lavelle was trying to make with that demonstration. Pressure itself does not change the reaction quotient. Rather, the change in concentration of the reactants is what affects the reaction quotient.

When you add an inert gas, you are increasing the pressure in the container. But the concentration of your reactants is not changing (you still have the same number of reactant moles of gas in a fixed volume). So pressure is not the driving factor with La Chatalier's principle. But when you decrease the volume of the container you now have more moles of reactant per volume and now are increasing the concentration of reactant gas in the chamber. This is what causes a shift in the equilibrium

[005324438]

Pressure alone doesn't change the equilibrium constant. The reason there is a change when we "increase pressure" is actually due to the decrease in volume, and change in concentrations of those initial gases. Adding an inert gas that will have no effect on the reaction doesn't change the equilibrium concentrations because there is no change in initial concentration.

[AGaeta_2C]

I was confused on this, too. Is this thinking correct?:

Because the equilibrium constant is a ratio of product concentration (moles/volume) to reactant concentration at equilibrium, it is unaffected by increases in pressure (by adding an inert gas) as long as the volume stays the same.

Thank you:)