Question detail
When measuring the rate of a reaction, which of the following factors must be controlled to ensure valid results?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
AS practical skills and required practical activities
Question
- A. The concentration of reactants
- B. The color of the reactants
- C. The size of the reaction vessel
- D. The type of catalyst used
Answer
The concentration of reactants
Explanation
The correct option is The concentration of reactants. The concentration of reactants is the best answer because it directly supports the AQA A-Level Chemistry objective to required practical 3: investigate how rate changes with temperature. This reasoning is anchored to AS required practical activities in AS practical skills and required practical activities, and it separates required practical from similar A-Level ideas rather than relying on a vague recall statement. Other options are weaker if they use the wrong evidence, calculation, mechanism, observation, unit, or conclusion for this subtopic.
Common mistake
Misunderstanding Temperature's Effect on Reaction Rate
Students often believe that increasing temperature always increases reaction rate without considering the specific reaction conditions.
To accurately assess how temperature affects reaction rate, use the formula for rate change: Rate ∝ 1/Temperature. For example, if the temperature increases from 20°C to 40°C, substitute into the formula to find the new rate. Calculate the rate change to conclude how the reaction rate is affected by temperature.
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