The reaction of hydrogen and iodine monochloride is given as: $\mathrm{H}_{2(g)}+2 \mathrm{ICl}_{(g)} \rightarrow 2 \mathrm{HCl}_{(g)}+\mathrm{I}_{2(g)}$ This reaction is of first order with respect to $\mathrm{H}_{2(g)}$ and $\mathrm{lCl}_{(g)+}$ following mechanisms were proposed Mechanism A:…

Question

The reaction of hydrogen and iodine monochloride is given as:
$\mathrm{H}_{2(g)}+2 \mathrm{ICl}_{(g)} \rightarrow 2 \mathrm{HCl}_{(g)}+\mathrm{I}_{2(g)}$
This reaction is of first order with respect to $\mathrm{H}_{2(g)}$ and $\mathrm{lCl}_{(g)+}$ following mechanisms were proposed
Mechanism A:
$\mathrm{H}_{2(g)}+2 \mathrm{ICl}_{(g)} \rightarrow 2 \mathrm{HCl}_{(g)}+\mathrm{H}_{2(g)}$
Mechanism B:
$\begin{aligned}
& \mathrm{H}_{2(g)}+\mathrm{ICl}_{(g)} \rightarrow \mathrm{HCl}_{(g)}+\mathrm{HI}_{(g)} \text { :slow } \\
& \mathrm{Hl}_{(g)}+\mathrm{lCl}_{(g)} \rightarrow \mathrm{HCl}_{(g)}+\mathrm{l}_{2(g)} \text {; fast }
\end{aligned}$
Which of the above mechanism(s) can be consistent with the given information about the reaction?

Aicharya · Accepted Answer

The slowest step is the rate determining step thus the mechanism $\mathrm{B}$ will be more consistent because it involve one molecule of $\mathrm{H}_2$ and one molecule of ICl. It can be expressed as
$r=k\left[\mathrm{H}_2\right][\mathrm{ICl}]$
Related Theory
The rate determining step in a reaction mechanism is characterised by high activation energy. Usually, the first step is the slow step since it has the highest activation energy.

The reaction of hydrogen and iodine monochloride is given as: $\mathrm{H}_{2(g)}+2 \mathrm{ICl}_{(g)}…

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