Question

Write the effect of catalyst on the rate of reaction.

Hint:

A catalyst offers an alternative path of lower activation energy; it speeds the reaction but does not shift the equilibrium.

Answer 1

Step 1: What a catalyst is.
A catalyst is a substance that increases the rate of a chemical reaction but is itself chemically unchanged in mass and composition at the end of the reaction.

Step 2: How it increases the rate.
A catalyst provides an alternative reaction path (a new mechanism) that has a lower activation energy \( (E_a) \) than the uncatalysed path. Because more colliding molecules now have energy equal to or greater than this lowered \( E_a \), the fraction of effective collisions rises and the rate increases.

Step 3: Effect on forward and backward reactions.
A catalyst lowers the activation energy of both the forward and the backward reaction by the same amount. Hence it speeds up both equally.

Step 4: Effect on equilibrium and thermodynamics.
Since it accelerates forward and backward reactions equally, a catalyst does not change the position of equilibrium or the value of the equilibrium constant. It only helps the equilibrium to be reached faster. It also does not change \( \Delta H \) or \( \Delta G \) of the reaction.

Final answer: A catalyst increases the rate of reaction by lowering the activation energy through an alternative path, without altering the enthalpy change or the equilibrium state.