Thallium(I) is oxidized by cerium(IV) as follows:
Tl+(aq) + 2Ce^4+(aq) > Tl^3+(aq) + 2Ce^3+(aq)
The elementary steps, in the presence of aqueous Mn(II), are as follows:
Step 1: Ce^4+ + Mn^2+ > Ce^3+ + Mn^3+
Step 2: Ce^4+ + Mn^3+ > Ce^3+ + Mn^4+
Step 3: Tl^+ + Mn^4+ > Tl^3+ + Mn^2+
(a) Identify the catalyst, intermediates, and the rate-determining step if the rate law is rate = k[Ce^4+][Mn^2+](b) Explain why the reaction is slow without the catalyst.(c) Classify the type of catalysis (homogeneous or heterogeneous).

A) Catalyst-Mn2+

Intermediates Mn3+ and Mn4+

Rate determining step is the reaction of Ce4+ with Mn2+

B) The reaction will be a termolecular reaction in the absence of the catalyst. It will be difficult for the two Ce2+ and Ti+ to collide in the correct orientation for reaction to occur in the absence of the catalyst hence the reaction will be slow in the absence of the catalyst.

C) Both catalyst and reactants are ions in solution hence it is a homogeneous catalysis

Explanation:

The catalyst is the specie that is regenerated at the end of a reaction. This specie is Mn2+.

Intermediates are transient species that only occur in elementary steps of a complex reaction mechanism.

The species involved in the rate determining step enter into the rate equation since the rate determining step is the slowest step in a complex reaction mechanism and determine the overall rate of reaction. The rate equation rate = k[Ce^4+][Mn^2+] confirms that the first step is the rate determining step in the overall reaction mechanism.