Chemical Kinetics - Result Question 33
####33. The reaction of hydrogen and iodine monochloride is given as:
[2007]
$H_2(g)+2 ICl(g) \longrightarrow 2 HCl(g)+I_2(g)$
The reaction is of first order with respect to $H_2(g)$ and $ICI(g)$, following mechanisms were proposed.
Mechanism $A$ :
$H_2(g)+2 ICl(g) \longrightarrow 2 HCl(g)+I_2(g)$
Mechanism B:
$H_2(g)+ICl(g) \longrightarrow HI(g)$; slow
$HI(g)+ICl(g) \longrightarrow HCl(g)+I_2(g)$; fast
Which of the above mechanism(s) can be consistent with the given information about the reaction?
(a) $A$ and $B$ both
(b) neither $A$ nor $B$
(c) $A$ only
(d) $B$ only
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Solution:
- (d) As the slowest step is the rate determining step thus the mechanism $B$ will be more consistent with the given information. Also because it involve one molecule of $H_2$ and one molecule of $ICl$, it can be expressed as :
$ r=k[H_2][ICl] $
Which shows that the reaction is of first order w.r.t. both $H_2$ & ICl.
