Question

The rate law of the reaction,

\[\ce{2NO2_{(g)} + F2_{(g)} -> 2NO2F_{(g)}}\], has been found to be Rate = k[NO₂] [F₂]. During the progress of the reaction, the transient existence of F atom has been confirmed. Postulate a mechanism for the reaction.

Answer 1

Overall reaction:

\[\ce{2NO2_{(g)} + F2_{(g)} −> 2NO2F_{(g)}}\]

Experimental rate law:

Rate = k[NO₂][F₂]

Observation:

Transient existence of fluorine atom (F) detected during reaction.

Postulated mechanism:

Step 1 (Sloe-rate determining step):

\[\ce{NO2 + F2 -> NO2F + F}\]

Bimolecular collision between NO₂ and F₂.

Rate = k1[NO₂][F₂] - matches the experimental rate law.

Produces an F atom as an intermediate.

Step 2 (Fast-rate determining step):

\[\ce{NO2 + F -> NO2F}\]

Rapid reaction of F atom with another NO₂ molecule.

Net reaction:

\[\ce{2NO2 + F2 -> 2NO2F}\]