Identify the order of reaction if its rate constant is k = 2 × 10⁻²s⁻¹:

The correct option is First order.

To determine the order of a reaction from its rate constant, we need to analyze the units of the rate constant ($k$).

The general formula for the unit of a rate constant is given by:
$\text{Unit of}k={\left(\text{mol},·,{\text{L}}^{-1}\right)}^{1-n}·{\text{s}}^{-1}$
where $n$ represents the order of the reaction.

Given in the question, the rate constant is:
$k=2\times {10}^{-2}{\text{s}}^{-1}$

Comparing the unit of the given rate constant, which is ${\text{s}}^{-1}$, with the general unit formula:
${\left(\text{mol},·,{\text{L}}^{-1}\right)}^{1-n}·{\text{s}}^{-1}={\text{s}}^{-1}$

This equality holds true when the term ${\left(\text{mol},·,{\text{L}}^{-1}\right)}^{1-n}$ becomes equal to 1. This happens when the exponent is zero:
$1-n=0$
$n=1$

Since $n=1$, the reaction is of the first order.