A-LevelChemistryChemical energetics9701/12 · Oct/Nov 2010 · 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

✓ Correct answer

D: +352 kJ mol⁻¹

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Topic: Chemical energetics, A-Level Chemistry (syllabus 9701). Multiple choice, 1 mark.
Source: A-Level Chemistry, Oct/Nov 2010 Paper 1 Variant 2, question 8.

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