Question detail
Calculate the entropy change (ΔS) for a reaction where the standard entropies of the reactants are 200 J/(mol·K) and 300 J/(mol·K), and the products have a standard entropy of 500 J/(mol·K).
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Thermodynamics (A-level only)
Question
- A. 200 J/(mol·K)
- B. 0 J/(mol·K)
- C. 100 J/(mol·K)
- D. 300 J/(mol·K)
Answer
200 J/(mol·K)
Explanation
The correct option is 200 J/(mol·K). 200 J/(mol·K) is the best answer because it directly supports the AQA A-Level Chemistry objective to calculate entropy changes from standard entropy data. This reasoning is anchored to Entropy and Gibbs free energy (A-level only) in Thermodynamics (A-level only), and it separates entropy 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 Entropy Calculation
Students often confuse the concept of entropy with other thermodynamic quantities and fail to apply the correct formula for calculating entropy changes.
To calculate entropy changes, use the formula ΔS = ΣS(products) - ΣS(reactants). Substitute the standard entropy values for the products and reactants, perform the calculation, and express the answer in J/K.
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