What effect does a catalyst have on activation energy and the rate of a reaction?

What effect does a catalyst have on activation energy and the rate of a reaction?

• A. Lowers activation energy and increases rate without changing ΔH.
• B. Increases activation energy and increases rate.
• C. Lowers activation energy and changes ΔH.
• D. Increases both activation energy and enthalpy.

Answer: (A)

A catalyst lowers the energy barrier for the reaction, providing an alternative pathway with a smaller activation energy. Because the barrier is easier to overcome, more molecules can react at the same temperature, so the reaction rate increases. The overall enthalpy change (ΔH) remains the same because catalysts don’t alter the thermodynamics of the reaction; they’re not consumed and don’t change the energies of reactants or products. So the best description is: it lowers activation energy and increases the rate without changing ΔH.

A catalyst lowers the energy barrier for the reaction, providing an alternative pathway with a smaller activation energy. Because the barrier is easier to overcome, more molecules can react at the same temperature, so the reaction rate increases. The overall enthalpy change (ΔH) remains the same because catalysts don’t alter the thermodynamics of the reaction; they’re not consumed and don’t change the energies of reactants or products. So the best description is: it lowers activation energy and increases the rate without changing ΔH.