Question detail
For the reaction A → products, the rate equation is given as rate = k[A]². If the rate constant k is found to be 0.5 mol⁻²dm⁶s⁻¹, what is the unit of the rate of reaction?
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Question
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Topic
Rate equations (A-level only)
Question
For the reaction A → products, the rate equation is given as rate = k[A]². If the rate constant k is found to be 0.5 mol⁻²dm⁶s⁻¹, what is the unit of the rate of reaction?
Answer
The unit of the rate of reaction is mol/dm³/s.
Explanation
The rate of reaction is defined as the change in concentration over time. Given the rate equation, the units can be derived from the equation: rate = k[A]². Therefore, the unit of rate is mol/dm³/s, consistent with the units of k and concentration.
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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