CHEMISTRY · Single correct · A Level · Chemistry · Kinetics · Kinetics
Problem
Consider the two-step conversion X → Z. Energies are given relative to the reactants (X):
• Transition state 1: 90 kJ
• Intermediate: 25 kJ
• Transition state 2: 60 kJ
• Products (Z): −40 kJ
Which statement correctly identifies the rate-determining step?
(a) Step 2, because its activation energy is only 35 kJ.
(b) Step 2, because its transition state is 60 kJ above the reactants.
(c) Step 1, because its transition state is 90 kJ above the reactants.
(d) Step 1, because its intermediate is higher in energy than the products.