Adding a catalyst changes a reaction's energy diagram in which way?

Core Concept

A catalyst offers an alternative pathway through a lower-energy transition state, so the curve's peak drops for the forward and reverse directions alike. The reactant and product levels are untouched, so ΔH is unchanged: catalysts alter rate, never thermodynamics. The reaction reaches the same equilibrium position, only faster. The barrier shrinks but never vanishes, because every pathway keeps some barrier.