The uncatalyzed decomposition of compound Z proceeds through the sequence Z → Z* → Y, where Z* is a reactive intermediate. A researcher tabulates the relative potential energies shown below.
Species
Potential Energy / kJ mol⁻¹
Z (reactant)
0
Transition State (uncatalyzed)
95
Z* (intermediate)
25
Y (product)
–10
The same reaction is studied in the presence of a catalyst C that lowers the energy of the transition state to 60 kJ mol⁻¹ but leaves all other species unchanged.
(a) Sketch, on qualitative axes of potential energy versus reaction coordinate, separate profiles for the catalyzed and uncatalyzed pathways, clearly labeling all key points and relative heights.
(b) Using the uncatalyzed data, calculate the activation energy for the reverse conversion Y → Z*.
(c) Calculate the new value of that reverse activation energy when catalyst C is present.
(d) Explain whether the catalyst is expected to alter the numerical value of the equilibrium constant for the overall reaction Z ⇌ Y. Support your answer with energetic reasoning.