Question

Which of the following is affected by catalyst?

• A. $∆\mathrm{H}$
• B. $∆\mathrm{S}$
• C. $∆\mathrm{G}$
• D. ${\mathrm{E}}_{\mathrm{a}}$

Answer 1

The correct option is D

${\mathrm{E}}_{\mathrm{a}}$

The explanation for the correct option

(D): ${\mathrm{E}}_{\mathrm{a}}$

• Catalyst is a substance that changes the rate of a chemical reaction but itself remains unchanged.
• For a reaction to proceed, the particles of reacting molecules must collide with each other. Also, the colliding of particles must have enough energy to break the old bonds. This amount of energy possessed by reactant molecules is called activation energy.
• Hence, activation energy (${\mathrm{E}}_{\mathrm{a}}$) is the minimum energy possessed by particles to collide to proceed a chemical reaction.
• Catalysts speed up the reaction by lowering the activation energy of the particles.
• Therefore, ${\mathrm{E}}_{\mathrm{a}}$ is affected by the catalysts.

The explanation for the incorrect options:

(A) The catalyst has no effect on the enthalpy change ($∆\mathrm{H}$) of the reaction.

(B) The catalyst has no effect on the entropy change ($∆\mathrm{S}$) of the reaction.

(C) The catalyst has no effect on the Gibb's free energy ($∆\mathrm{G}$) of the reaction.

Hence, the correct option is (D), Activation energy is affected by the catalyst.