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. I only
B. II only
C. I and II both
D. neither I nor II

Answer

B

Explanation

Since the given reaction is first order with respect to `H_(2)` and `ICl`, the slow step should involve 1 molecule of `H_(2)` and 1 molecule of `ICl`. Hence `II` is the correct mechanism.