A-LevelChemistryChemical energeticsOct/Nov 2010Paper 1 Q81 Mark
Use of the Data Booklet is relevant to this question. The enthalpy change of formation, ∆H_f, of hydrated calcium ions is the enthalpy change of the following reaction. Ca(s) + aq – 2e⁻ → Ca²⁺(aq) The following enthalpy changes are not quoted in the Data Booklet. Ca(s) → Ca(g) ∆H = 177 kJ mol⁻¹ Ca²⁺(g) + aq → Ca²⁺(aq) ∆H_hyd = -1565 kJ mol⁻¹ What is the enthalpy change of formation of hydrated calcium ions?
A-1388 kJ mol⁻¹
B-798 kJ mol⁻¹
C-238 kJ mol⁻¹
D+352 kJ mol⁻¹
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The correct answer is D. This question tests the candidate's understanding of chemical energetics within the Chemistrysyllabus. The examiner's mark scheme requires...
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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...
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