Mechanism of a hypothetical reactionX2+Y2→2XYis given below :(i) X2→X+X(fast)(ii)  X+Y2⇌XY+Y (slow)(iii) X + Y ➔ XY (fast)The overall order of the reaction will be

Note : Correct the reactions given in question as X2⇌X+X                   (fast) X+Y2⟶XY+Y          (Slow)  Slow step is the rate determining step.   Rate =K[X]Y2             (i)  Equilibrium constant for fast step, K=[X]2X2 [X]=KX2  By substituting [X] in equation (i), we get   Rate =kKX2Y2=k'X21/2Y2 ∴ Order of reaction =12+1=32=1.5