Question detail
Determine the heat energy change when 200 g of water is cooled from 100 °C to 0 °C. The specific heat capacity of water is 4.18 J/g°C.
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Energetics
Question
- A. -83,600 J
- B. -80,000 J
- C. -75,000 J
- D. -70,000 J
Answer
-83,600 J
Explanation
The correct option is -83,600 J. -83,600 J is the best answer because it directly supports the AQA A-Level Chemistry objective to use appropriate units and significant figures in enthalpy calculations. This reasoning is anchored to Calorimetry and enthalpy measurements in Energetics, and it separates figures 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 Units in Enthalpy Calculations
Students often forget to convert units properly when calculating enthalpy changes, leading to incorrect results.
Always ensure that mass is in grams, specific heat capacity is in J/g°C, and temperature change is in °C. Use the formula q = mcΔT, substituting the correct values to find the heat energy transferred. For example, if m = 50 g, c = 4.18 J/g°C, and ΔT = 10°C, then: q = 50 g × 4.18 J/g°C × 10°C = 2090 J. Therefore, the heat energy transferred is 2090 J.
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