The three experimental data for determining the differential rate of reaction $2 NO_{(g)} + Cl_{2(g)} \rightarrow 2 NOCl_{(g)}$ at a definite temperature are given below.
$(a)$ Calculate the order of reaction.
$(b)$ Calculate the value of the rate constant.

(A) The rate law expression is given by $Rate = k[NO]^x[Cl_2]^y$.
By comparing the experimental data (assuming standard data where rate doubles with $Cl_2$ and quadruples with $NO$):
Order with respect to $NO$ is $x = 2$,and order with respect to $Cl_2$ is $y = 1$.
Total order of reaction $= x + y = 2 + 1 = 3$.
$(b)$ Using the rate law $Rate = k[NO]^2[Cl_2]$,the rate constant $k$ is calculated by substituting the values from any experimental set:
$k = \frac{Rate}{[NO]^2[Cl_2]}$.
The units for the rate constant for a third-order reaction are $L^2 \ mol^{-2} \ s^{-1}$.