A-LevelChemistryChemical energeticsMay/June 2011Paper 1 Q71 Mark
Titanium occurs naturally as the mineral rutile, TiO2. One possible method of extraction of titanium is to reduce the rutile by heating with carbon. TiO2(s) + 2C(s) → Ti(s) + 2CO(g) The standard enthalpy changes of formation of TiO2(s) and CO(g) are –940 kJ mol⁻¹ and -110 kJ mol⁻¹ respectively. What is the standard enthalpy change of this reaction?
A-830 kJ mol⁻¹
B-720 kJ mol⁻¹
C+720 kJ mol⁻¹
D+830 kJ mol⁻¹
✓ Correct Answer
The correct answer is C: +720 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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