Nitric oxide reacts with oxygen to produce nitrogen dioxide.
` 2NO (g) +O_(2) (g) to 2NO_(2) (g)`
What is the predicted rate law and order if the mechanism is:
`(i) NO +O_(2) overset(K) hArr NO_(3) ` ( fast)
` (ii ) NO_(3) +NO overset(K_1) hArr NO_(2) +NO_2` ( slow)

Explanation

Since the slow step is the rate determining step, we have rate law as:
` (iii) ` rate ` =k_1 [NO_3 ][NO]`
from (i) `K =([NO_3])/([NO][O_2]) or [NO_3 ]=K [NO][O_2]`
Substituting the value of `[NO_3] `in (iii)
rate ` = k_1 xx K[NO][O_2][NO]=k_2 [NO]^2 [O_2]`
` therefore ` Order of reaction `= 2+1=3`