A-LevelChemistryChemical energeticsOct/Nov 2014Paper 1 Q71 Mark
In an experiment to calculate the enthalpy change of combustion of a fuel, 1.5g (0.0326 mol) of the fuel was used to heat 200 g of water. The temperature of the water rose from 25°C to 55°C. The specific heat capacity of water is 4.18 Jg⁻¹K⁻¹. There is significant heat loss in this experiment. Therefore, the experimental value for the enthalpy change of combustion, ∆H_c, of the fuel will be different from the theoretical value. Using the information above, what is the experimental value for the enthalpy change of combustion, ∆H_c, of the fuel?
A-1410 kJ mol⁻¹
B-769 kJ mol⁻¹
C-30.7 kJ mol⁻¹
D-16.7 kJ mol⁻¹
✓ Correct Answer
The correct answer is B: -769 kJ mol⁻¹
📋 Examiner Report & Trap Analysis
Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
🎯 Mark Scheme Breakdown
Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.
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