[dorebase2006]

1. The problem statement, all variables and given/known data
Consider the following mechanism:
(1) ClO^- (aq) + H₂O (l)  HClO (aq) + OH^- (aq) [fast]
(2) I^- (aq) + HClO (aq)  HIO (aq) + Cl^- (aq) [slow]
(3) OH^- (aq) + HIO (aq)  H₂O (l) + IO^- (aq) [fast]

Is the mechanism consistent with the actual rate law: rate = k[ClO^-][I^-]

2. The attempt at a solution
I can't eliminate the intermediate OH^- in my rate law. As far as I know, since the second step is slow, my rate should come from there, so rate = k₂ [I^-][HClO]. Then I use the equilibrium (1) to express [HClO] in terms of [reactant]'s, but apparently [OH^-] is there, and I don't know how to continue with this.

Another problem with which I also have the same trouble is the following proposed mechanism for the sulfonation of benzene:
(1) H₂SO₄  H₃O⁺ + HSO₄^- + SO₃ [fast]
(2) SO₃ + C₆H₆  H(C₆H₅⁺)SO₃^- [slow]
(3) H(C₆H₅⁺)SO₃^- + HSO₄^-  C₆H₅SO₃^- + H₂SO₄ [fast]
(4) C₆H₅SO₃^- + H₃O⁺  C₆H₅SO₃H + H₂O [fast]

Thanks in advance!