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The reaction A2 + B2 → 2 AB follows the mechanism A2 ⇌ A + A (fast) A + B2 → AB + B (slow) A + B → AB (fast) The overall order of the reaction is :
- 1.5
- 3
- 2.5
- 2
Correct answer: 1.5
Solution
The overall order of the reaction is determined by the rate-determining step, which is the slow step involving A and B2. Since this step is first order in A and second order in B2, the overall order is 1 (from A) + 2 (from B2) = 3, but considering the fast equilibrium step that produces A, the effective concentration of A is halved, leading to an overall order of 1.5.
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