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Chemical Kinetics

Question
CBSEENCH12006259

Nitrogen dioxide reacts with fluorine to give

2NO2+F2  2NO2F

The kinetic of this reaction is explained by the following steps.

(i) NO2 + F→ 2NO2F (slow)
(ii) NO2 + F → NO2F (fast)

What is the predicted law?

Solution
For the given reaction

2NO2+F2  2NO2F

This reaction involves 3 molecules and proceeds in two steps:

(i) NO2 + F2 → 2NO2F + F (slow)
(ii) NO2 + F → NO2F (fast)

The first stage being slow is the rate determining step. The rate is

Rate = dNO2Fdt = kNO2 F2

This indicates that the reaction is of second order.