Mechanism of a hypothetical reaction X _ 2 + Y _ 2 → 2XY is given...

The solution of this question is given by assuming step $( i )$ to be reversible which is not given in question

Overallrate = Rateofsloweststep ( ii )$<br /><br />$= k\left[X\right]\left[{Y}_{2}\right]$......$( i )$<br /><br />K=rate constant of step$( ii )$<br /><br />Assuming step$( i )$to be reversible, its equilibrium constant,<br /><br />${k}_{eq} = \dfrac{{\left[X\right]}^{2}}{\left[{X}_{2}\right]} ⇒ \left[X\right] = {k}_{eq}^{\dfrac{1}{2}}{\left[{X}_{2}\right]}^{\dfrac{1}{2}}$.....$( ii )$<br /><br />Put$( ii )$in$( i )$<br /><br />Rate$= k{k}_{eq}^{\dfrac{1}{2}}{\left[{X}_{2}\right]}^{\dfrac{1}{2}}\left[{Y}_{2}\right]$<br /><br />Overall order$= \dfrac{1}{2} + 1 = \dfrac{3}{2}