How are these equilibrium quantities affected by the initial amount of x(g) placed in the container? assume constant temperature?

The equilibrium can be affected when there is a change of concentration, pressure or temperature of the system. Since it is mentioned that the temperature is constant, and the parameter being focused on is the initial amount, that should be the concentration factor. It depends where substance X is placed in the reaction. If it is a reactant (left side), then the equilibrium would shift and favor the forward reaction. If it is a product (right side), then the equilibrium would shift and favor the reverse reaction.

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