Which of the following actions does NOT affect the equilibrium of a reaction?

Explanation

The equilibrium of a reaction can be changed by several factors. If you recall Le Châtelier's principle, you can rule out any answer choice that would shift the direction of an equilibrium. Adding or subtracting heat would shift the equilibrium based on the enthalpy change of the reaction. Adding reactant concentration would shift the equilibrium in the direction of the product, and the opposite would occur if concentrations were decreased. Changing the volume of a reactant would change its concentration, so that would have the same effect. Only (B), adding or removing a catalyst, would change the reaction rate without changing where the equilibrium lies.