Question detail
What is the purpose of measuring enthalpy change in a reaction?
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. To calculate the energy absorbed or released during a reaction
- B. To determine the temperature of the reactants
- C. To measure the volume of gas produced
- D. To assess the rate of the reaction
Answer
To calculate the energy absorbed or released during a reaction
Explanation
The correct option is To calculate the energy absorbed or released during a reaction. To calculate the energy absorbed or released during a reaction is the best answer because it directly supports the AQA A-Level Chemistry objective to required practical 2: measure an enthalpy change. 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
Incorrect Measurement of Enthalpy Change
Students often forget to account for the specific heat capacity of the solution when calculating the enthalpy change, leading to inaccurate results.
To fix this, remember to use the formula q = mcΔT, where q is the heat energy, m is the mass of the solution, c is the specific heat capacity, and ΔT is the change in temperature. Substitute the values correctly and ensure to include units in your final answer. For example, if you have 100 g of water (m = 100 g), with a specific heat capacity of 4.18 J/g°C (c), and a temperature change of 10°C (ΔT), the calculation would be: q = 100 g × 4.18 J/g°C × 10°C = 4180 J. Thus, the enthalpy change is 4180 J.
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