Describe why the enthalpy of a reaction remains unchanged when a catalyst is used in a reaction.

Explanation

In a catalysed reaction, the energy states or enthalpies of the reactants as well a products remain unchanged. Therefore, `Delta_(H)(H_(p)-H_(r))` does not change in the reaction. The purpose of catalyst in a reaction is simply to lower the height of the energy barrier for the reaction and as a result. The reaction rate increases.