Question

Consider the reaction :
$C{l}_{2(aq)}+H_2{S}_{(aq)}\to S_{(s)}+2H_{(aq)}^{+}+2C{l}_{(aq)}^{-}$
The rate equation for this reaction is rate $=k[C{l}_2][H_{2}S]$
Which of these mechanisms is/are consistent with this rate equation ?
$\left(A\right)C{l}_2+H_{2}S\to H^{+}+C{l}^{-}+C{l}^{+}+H{S}^{-}$ (slow)
$C{l}^{+}+H{S}^{-}\to H^{+}+C{l}^{-}+S$ (fast)
$\left(B\right)H_{2}S\rightleftharpoons H^{+}+H{S}^{-}$ (fast equilibrium)
$C{l}_2+H{S}^{-}\to 2C{l}^{-}+H^{+}+S$ (slow)

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

Answer 1

Answer: (D)

Rate equation is to be derived wrt slow
Step $\therefore$ from mechanism (A)
Rate $=k[C{l}_2][H_{2}S]$