In the graph above, the activation energy of the catalyzed reaction is

Correct answer: 100 kJ

Explanation: In an energy–time (or progress) profile, the activation energy is the vertical energy gap between the reactants and the peak of the curve. The catalyzed pathway is the curve with the lower peak (dashed). From the graph, reactants start at about 100 kJ and the catalyzed peak is about 200 kJ. Therefore,

E_a(catalyzed) = 200 kJ − 100 kJ = 100 kJ.

• 100 kJ — Correct.
• 300 kJ — Approximate peak of the uncatalyzed path, not E_a for the catalyzed one.
• 250 kJ — Not supported by the graph.
• 200 kJ — Peak value, but E_a is the difference from reactants (200 − 100), not 200 itself.