Consider the reaction: 

H₂ (g) + 2 ICl (g) → I₂ (g) + 2 HCl (g) 

The observed rate law is Rate = k [H₂][ICl]. A proposed mechanism for this reaction is: 

 

Step 1: H₂ (g) + ICl (g) → HI (g) + HCl (g) 

Step 2: HI (g) + ICl (g) → I₂ (g) + HCl (g) 

 

a) Which step is the rate-determining step?  

b) What is the intermediate in this proposed reaction mechanism? 

c) Draw an energy diagram for this proposed mechanism. Label the reactants, products, intermediate(s), and activation barrier(s). Both steps are exothermic.