Question

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

The correct option is D A only

Rate equation is to be derived with respect to slow step.
From mechanism (A), Rate $=k\left[C{l}_2\right]\left[H_{2}S\right]$