What is the rate law of NO2 gas​

The rate law cannot be defined based on just the formula given.

Explanation:

In the world of chemical kinetics there are four major concepts that are used to define the speed of a reaction. These are Rate Averaging, Equation Stoichiometry, Experimental Rate Laws and Integrated Rate Laws for Orders of Reaction. Each topic requires a reference reaction that has been defined in terms of the definition of reaction rates whose data can be applied to the expression ...

Rate = ΔConcentration/Δtime

If you will provide a balanced equation then empirical relationships can be presented that describe the consumption rate of reactants and/or the formation products. For example:

Given Equation  2NO₂(g) => 2NO(g) + O₂(g)  and the measured rate of at least one component of the reaction, the following rate relationships can be defined:

Δ[NO₂(g)]/Δt = Δ[NO(g)]/Δt  (Since coefficients are equal then the relationship is 1:1),

Δ[NO₂(g)]/Δt =2· Δ[O₂(g)]/Δt  and

Δ[NO(g)]/Δt =2· Δ[O₂(g)]/Δt

Experimental Rate Law is based upon experimental observations of rxn rates as a function of molar concentration changes. The kinetic data is examined for 'Order of Rxn' and applied to the empirical rate law to obtain the numerical rate law.

Empirical Rate Law

Rate = k[NO₂(g)]ᵃ

k = rate constant

a = order of reaction

both are determined from experimentally observing rxn rate as a function of changing concentration of reactants.