Adding a catalyst to a reversible reaction before reaching equilibrium can speed up the attainment of equilibrium but does not affect the position of the equilibrium or the concentrations of the reactants and products at equilibrium.
A catalyst is a substance that increases the rate of a chemical reaction by providing an alternative reaction pathway with a lower activation energy. By lowering the activation energy, a catalyst allows the reactant molecules to more easily reach the transition state and undergo the chemical transformation.
When a catalyst is added to a reversible reaction before equilibrium, it increases the rates of both the forward and reverse reactions. As a result, the system reaches equilibrium more quickly compared to the situation without a catalyst.
However, it's important to note that the addition of a catalyst does not alter the equilibrium constant (K) for the reaction or change the concentrations of the reactants and products at equilibrium. The catalyst affects the kinetics of the reaction but not the thermodynamics.
In summary, adding a catalyst before equilibrium speeds up the attainment of equilibrium by accelerating the rates of the forward and reverse reactions. It does not alter the position of the equilibrium or the concentrations of the species involved at equilibrium.