Question detail
If the initial rate of a reaction doubles when the concentration of reactant A is doubled, what is the order of the reaction with respect to A?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Rate equations (A-level only)
Question
- A. 0
- B. 1
- C. 2
- D. 3
Answer
1
Explanation
The order of reaction is determined by how the rate changes with concentration. If doubling the concentration of A doubles the rate, the reaction is first order with respect to A, as the rate is directly proportional to the concentration.
Common mistake
Incorrect Rate Equation Prediction
Students often confuse the overall reaction equation with the rate-determining step when predicting the rate equation from a proposed mechanism.
To fix this, clearly identify the rate-determining step in the mechanism and use only the reactants involved in that step to write the rate equation. For example, if the rate-determining step is A + B → C, the rate equation would be rate = k[A][B], where k is the rate constant.
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