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The following mechanism has been propose...

The following mechanism has been proposed for the reaction of NO with `Br_(2)` to from NOBr.
`NO(g)+Br_(2)hArrNOBr_(2)(g)`
`NOBr_(2)(g)+NO(g)rarr2NOBr(g)`
If the second step is the rate determining step, the order of the reaction with respect to NO(g) is

A

2

B

0

C

`0.5`

D

1

Text Solution

Verified by Experts

The correct Answer is:
A
The overall reaction equation is
`2NO(g)+Br_(2)(g)rarr2NOBr(g)`
According to the rate determining step
Rate `=K_(2)[NOBr_(2)][NO]`
Now try to eliminate `NOBr_(2)` from the rate law by by looking at the first step, which is fast step, and reaches equilibrium. Writing the equilibrium constant we have
`K_(eqw.)+([NOBr_(2)])/([NO]Br_(2)]`
Substituting this expression into the rate law gives
Rate `=K_(2)K_(eq.)[NO][Br_(2)[NO]`
or Rate `=K'[NO]^(2)[Br_(2)]`
where `K'=K_(2)K_(eq.)` . notice that order of the reaction with respect to `NO` is two.
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