Question detail
In a practical experiment, a student observes that the time taken for a reaction to complete is halved when the temperature is raised from 25 °C to 75 °C. Which statement best describes this observation?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Rate of reaction
Question
- A. The reaction rate has doubled because the temperature increase has doubled the activation energy.
- B. The reaction rate has increased because the higher temperature increases the proportion of molecules with energy above the activation energy.
- C. The reaction rate has decreased because the higher temperature reduces the concentration of reactants.
- D. The reaction rate is unchanged; the observation is due to experimental error.
Answer
The reaction rate has increased because the higher temperature increases the proportion of molecules with energy above the activation energy.
Explanation
The correct answer is The reaction rate has increased because the higher temperature increases the proportion of molecules with energy above the activation energy.. This answer directly addresses the question: In a practical experiment, a student observes that the time taken for a reaction to complete is halved when the temperature is raised from 25 °C to 75 °C. Which statement best describes this observation? It matches the approved Chemistry 8462 learning objective and the linked subtopic. The other options are incorrect because they either change the rate, catalyst, reversible reaction, equilibrium, or graph context, or they do not answer the exact point being tested.
Common mistake
Temperature effect misinterpreted
Students often think that increasing temperature always increases the rate of reaction, even for reactions that are endothermic or have a temperature-dependent equilibrium shift.
Explain that while higher temperature generally increases reaction rate by providing more kinetic energy and higher collision frequency, it can also shift equilibria or favour reverse reactions in some cases. Clarify that the temperature dependence of the rate is described by the Arrhenius equation and that the effect is not universal for all reactions.
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