Question detail
What is the molar enthalpy change when 100 g of a substance releases 5000 J of heat energy?
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. -50.0 kJ/mol
- B. -25.0 kJ/mol (A-level cue 824a81dc distractor 1)
- C. -75.0 kJ/mol (A-level cue 824a81dc distractor 2)
- D. -100.0 kJ/mol (A-level cue 824a81dc distractor 3)
Answer
-50.0 kJ/mol
Explanation
The correct option is -50.0 kJ/mol. -50.0 kJ/mol is correct because it supports the objective: Use appropriate units and significant figures in enthalpy calculations.. The reasoning stays within Calorimetry and enthalpy measurements and avoids drifting into a similar A-Level Chemistry idea. This item is treated as conceptual revision rather than a formal calculation item because the validated answer is an explanation or option choice, not a worked numerical response.
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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