Analyze the generalized rate data:

$\mathrm{RX}+{\mathrm{M}}^{\ominus }⟶\text{ Product }$

Experiment	[RX] Substrate	[${\mathrm{M}}^{⊝}$] Attacking species	Rate
I	0.10 M	0.10 M	1.2 × 10-4
II	0.20 M	0.10 M	2.4 × 10-4
III	0.10	0.20 M	2.4 × 10-4
IV	0.20 M	0.20 M	4.8 × 10-4

The value of rate constant for the given experiment data is

From experiments I and II, when the concentration of [RX] becomes double ,rate also becomes double, so order w.r.t. (RX) =1.

Similarly, from experiments II and IV, when the concentration of ${\mathrm{M}}^{⊝}$ is doubled, rate also is doubled. So order w.r.t. [${\mathrm{M}}^{⊝}$] =1.

Hence, rate = k[RX] [${\mathrm{M}}^{⊝}$]                    . . . . (1)

So overall second order reaction.

From eq. (i)

$\begin{array}{l}1.2\times {10}^{-4}=k\left[0.1\right]\left[0.1\right]\\ \therefore k=1.2\times {10}^{-2}\end{array}$