A reaction mechanism consists of three elementary steps: (1) , (2) , (3) . Which step is the rate-determining step?
Answer
Step (2):
The correct answer is Step (2): — Step 4: State the answer: step (2) is the rate-determining step.
Step-by-step solution
- Step 1: Identify the rate law for the overall reaction from the mechanism; the slowest elementary step determines the rate law.
- Step 2: Examine each step’s speed: step (1) and step (3) are fast, while step (2) is slow.
- Step 3: Conclude that the slow step controls the overall rate, so it is the rate-determining step.
- Step 4: State the answer: step (2) is the rate-determining step.
Common mistake: Assuming the first or last step is rate-determining
Concept tested: Rate-determining step in a mechanism
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