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Mechanism of a hypothetical reaction X₂ + Y₂ → 2XY is 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:
- 2
- 0
- 1.5
- 1
Correct answer: 1.5
Solution
The overall order of the reaction is determined by the slowest step, which is step (ii). The order of this step is 1 (since one molecule of X reacts with one molecule of Y₂). However, since step (i) is fast, it can be considered as a part of the equilibrium, and the order of the reaction is determined by the slowest step, which is 1.5.
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