A two-step mechanism for the conversion of X to Y has the following activation…
CHEMISTRY · Single correct · AP · Chemistry · Kinetics · Kinetics
Problem
A two-step mechanism for the conversion of X to Y has the following activation energies measured relative to the reactants:
• Step 1: 60kJmol−1
• Step 2: 80kJmol−1
A catalyst lowers the activation energy of Step 2 by 30kJmol−1 but does not affect Step 1. Which statement is most consistent with the effect of the catalyst on the overall reaction rate?
(a) Step 2 remains the rate-determining step because, even after a 30kJ mol−1 reduction, its activation energy is still higher than that of Step 1.
(b) Both elementary steps are accelerated equally by the catalyst, so the overall rate and the rate law are unchanged.
(c) Step 1 becomes the rate-determining step because its activation barrier now exceeds that of Step 2.
(d) Neither step now limits the reaction because both activation energies have been lowered below the original highest barrier.