Question detail
What is the purpose of measuring an enthalpy change in a chemical reaction?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
A-level practical endorsement and required practical activities
Question
- A. To assess the energy changes during the reaction
- B. To determine the concentration of reactants
- C. To identify the products formed
- D. To calculate the rate of reaction
Answer
To assess the energy changes during the reaction
Explanation
The correct option is To assess the energy changes during the reaction. To assess the energy changes during the 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 A-level required practical activities in A-level practical endorsement and required practical activities, and it separates enthalpy 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 Enthalpy Change Measurement
Students often confuse the enthalpy change with the total heat released or absorbed during a reaction, neglecting to consider the specific heat capacity of the solution used.
To correctly measure the enthalpy change, 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. For example, if 100 g of water (c = 4.18 J/g°C) is heated from 20°C to 25°C, substitute into the formula: q = 100 g × 4.18 J/g°C × (25°C - 20°C) = 2090 J. Therefore, the enthalpy change is 2090 J. Keep the correction anchored to A-level required practical activities and the objective: Required practical 2: measure an enthalpy change.
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