Answer 1

2NO+O₂→2NO₂

Molecularity of reaction = 3

Answer 2

The molecularity of the reaction is 3.

Explanation : 

Molecularity : It is defined as the total number of reactant molecules taking part in the balanced equation of a reaction. It is a theoretical concept.

The given balanced chemical reaction is,

2NO_(g)+O_2(g)→2NO_2(g)

In this reaction, 2 NO molecules reacts with the 1 Oxygen molecule.Total number of reactant molecule = 2 + 1 = 3

Therefore, the molecularity of the reaction is 3.