2 NO(g) + O2(g) → 2 NO2(g)
The rate law for the above reaction is r = k[NO(g)]2
[O2(g)]
The order of the reaction = sum of the powers of the
concentration terms in the rate expression
                                  Â
= order with respect to NO(g) + order with respect to
O2(g)
                                  Â
= 2+1
                                  Â
= 3
So the overall order of the reaction is 3
Since the order of the reaction is 3 so it is third-order
reaction
Therefore option (d) is correct.
