Question detail
A reaction has the following initial rate data: [A] = 0.1 mol/dm³ gives a rate of 0.02 mol/dm³/s, and [A] = 0.2 mol/dm³ gives a rate of 0.08 mol/dm³/s. Determine the order of the reaction with respect to A.
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Question
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Style
Topic
Rate equations (A-level only)
Question
A reaction has the following initial rate data: [A] = 0.1 mol/dm³ gives a rate of 0.02 mol/dm³/s, and [A] = 0.2 mol/dm³ gives a rate of 0.08 mol/dm³/s. Determine the order of the reaction with respect to A.
Answer
The reaction is second order with respect to A.
Explanation
The order of reaction can be deduced by comparing the rates and concentrations. Doubling the concentration of A from 0.1 to 0.2 mol/dm³ results in a quadrupling of the rate from 0.02 to 0.08 mol/dm³/s, indicating a second-order dependence.
Common mistake
Incorrect Rate Equation Formation
Students often confuse the order of reaction with the coefficients in the balanced equation when writing rate equations.
To write the correct rate equation, identify the order of each reactant based on experimental data, not the coefficients. For example, if the rate law is rate = k[A]^2[B]^1, this indicates that the reaction is second order with respect to A and first order with respect to B. Ensure to use the correct orders derived from initial rate data.
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