Question

Consider the reaction : $Cl_{2(aq)} + H_2S_{(aq)} \to S_{(s)} + 2H^+_{(aq)} + 2Cl^-_{(aq)}$ The rate equation for this reaction is rate $= k [Cl_2] [H_2S]$ Which of these mechanisms is/are consistent with this rate equation ? $\left(A\right) Cl_{2} + H_{2}S \to H^{+} + Cl^{-} + Cl^{+} + HS^{-}$ (slow) $Cl^{+} + HS^{-} \to H^{+} + Cl^{-} + S$ (fast) $\left(B\right) H_{2}S \rightleftharpoons H^{+} + HS^{-}$ (fast equilibrium) $Cl_{2} + HS^{-} \to 2Cl^{-} + H^{+} + S$ (slow)

• A. $B$ only
• B. Both $A$ and $B$
• C. Neither $A$ nor $B$
• D. $A$ only

Answer 1

Answer: (D)

$A$ only

Answer 2

Rate equation is to be derived wrt slow Step $\therefore$ from mechanism (A) Rate $= k[Cl_2] [H_2S]$