Shown in the mechanism below is the catalyzed decomposition of hydrogen peroxide. Determine the catalyst/s and the reaction intermediate/s.

Step 1. H₂O₂ + 2 Br^- + 2 H⁺ → 2 H₂O + Br₂

Step 2. H₂O₂ + Br₂ → 2 Br^- + 2 H⁺ + O₂

Consider the following reaction mechanism: 

OCl^–(aq) + H₂O(l) ⇌ HOCl(aq) + OH^–(aq)       (fast equilibrium)

I^–(aq) + HOCl(aq) → HOI(aq) + Cl^–(aq)           (slow)

HOI(aq) + OH^–(aq) → H₂O(l) + OI^–(aq)           (fast)

Determine the catalyst and intermediate(s).

A. No catalyst, intermediate = HOCl, HOI, OH^–

B. No catalyst, intermediates = H₂O, HOCl, HOI, OH^–

C. Catalyst = H₂O, intermediates = HOCl, HOI, OH^–

D. Catalyst = H₂O, intermediate = HOCl, HOI

The reaction H₂(g) + I₂(g) → 2 HI(g) was thought to occur via a two-step mechanism:

Step 1: I₂(g) ⇌ 2 I(g) (fast equilibrium)
Step 2: 2 I(g) + H₂(g) → 2 HI(g) (slow)

Determine the rate law for the reaction.

Consider the reaction below:

A + C₂ → AC₂

The reaction is first-order in A and first-order in C₂.

Two mechanisms are proposed for the reaction: 

Mechanism 1 (single-step):

A + C₂ → AC₂  

Mechanism 2:

B + C₂ → BC + C slow

A + BC → AB + C fast

AB +  2 C → AC₂ + B fast

Are both mechanisms valid? If yes why? 

Consider this three-step mechanism for a reaction:

Cl₂ (g) k₁⇌k₂ 2 Cl (g) Fast

Cl (g) + CHCl₃ (g) →k₃ HCl (g) + CCl₃ (g) Slow

Cl (g) + CCl₃ (g) →k₄ CCl₄ (g) Fast

c. What is the predicted rate law?