What is the effect of adding a catalyst on (a) Activation energy (Ea), and (b) Gibbs energy (ΔG) of a reaction?

(a) On adding a catalyst, activation energy decreases if the added catalyst is a positive catalyst and if the added catalyst is a negative catalyst then the activation energy increases. (b) Gibbs energy is a state function which depends only upon the initial and final states of the reaction; hence, there will not be any effect on the presence of a catalyst on Gibbs energy.