The reaction obey I order with respect to `H_(2)` and `ICl` both.
`H_(2) (g) + 2ICl(g) rarr 2 HCl(g) + I_(2) (g)`
Which of the following mechanism is in consistent with the given fact ?
Mechanism A: `H_(2) (g) + 2Cl rarr 2HCl(g) + I_(2)(g)`
Mechanism B: (i) `H_(2)(g) + ICl(g) overset ("slow")rarr HCl(g) + HI(g)`
(ii) `HI(g) + ICl(g) rarr HCl(g) + I_(2)`

Options

A. Neither A nor B
B. A only
C. B only
D. A and B both

Answer

C

Explanation

According to mechanism `A` , which proceeds through an elementary reaction, should be of first order with respect to `H_(2)(g)` and of second order with respect to `ICI` . Therefore, mechanism `A` is ruled out. On the other hand, there are two steos in mechanism `B` Rate of overall reaction is controlled by the slow step which involves one molecule of `H_(2)` and one molecule of `ICI` i.e., the law should be
Rate `=k[H_(2)][ICI]`
Therefore, mechanism `B` is consistant with the given in formation