Question

Consider the reaction,
`Cl_(2)(aq) + H_(2)S(aq) rarr S(s) + 2H^(+) (aq) + 2Cl^(-)(aq)`
The rate equation for this reaction is,
Rate `=k [Cl_(2)][H_(2)S]`
Which of these mechanisms is`//`are consistent with this rate equation ?
(I) `Cl_(2) + H_(2)S rarr H^(+) + Cl^(-) + Cl^(+) + HS^(-)` (slow)
`Cl^(+) + HS^(-) rarr H^(+) + Cl^(-) + S` (fast)
(II) `H_(2)S hArr H^(+) +HS^(-)` (fast equilibrium)
`Cl^(+) + HS^(-) rarr 2 Cl^(-) + H^(+) + S` (slow)
A. A only
B. B only
C. Both A and B
D. Neither A nor B

Answer 1

Correct Answer - a
For A
Rate = `k (Cl_(2)) (H_(2)S)` (By slow step)
For B
Rate = `k[Cl_(2)][HS^(-)]`
`k_(eq) = ([H^(+)][HS^(-)])/([H_(2)S])` (according to equilibrium)
Rate = `k[Cl_(2)] (k_(eq)[H_(2)S])/([H^(+)])`
Rate = `kk_(eq)[Cl_(2)] ([H_(2)S])/([H^(+)])` .