0
2
1.5
1
Take reaction (i) and (iii) to be equilibrium reaction where value of kf >>> kb
Therefore, [X]²/[X2] = K'e ⇌ [X] = K'e⁰·⁵ × [X2]⁰·⁵ − (A)
Since reaction (ii) is the slowest step, so the rate of this reaction will be reaction rate for the main reaction.
⇌ r = Ke[X][Y2] − (B)
Substituting equation(A) in equation(B)
We get r = Ke × K'e⁰·⁵[X2]⁰·⁵[Y2]
Let Ke × K'e = K
⇌ r = K[X2]⁰·⁵[Y2]
Hence, order of reaction is 1 + 0.5 = 1.5