The dissolution of ionic compound MX in water can be viewed as the sum of three…

CHEMISTRY · Multi-part · A Level · Chemistry · Thermodynamics · Thermodynamics

Problem

The dissolution of ionic compound MX in water can be viewed as the sum of three elementary energy changes. • Breaking the MX lattice: ΔH1=+788 kJ⋅mol−1\Delta H_1 = +788\,\text{kJ}\cdot\text{mol}^{-1}, ΔS1=−10 J⋅mol−1⋅K−1\Delta S_1 = -10\,\text{J}\cdot\text{mol}^{-1}\cdot\text{K}^{-1} • Reorganizing surrounding water molecules: ΔH2=+15 kJ⋅mol−1\Delta H_2 = +15\,\text{kJ}\cdot\text{mol}^{-1}, ΔS2=−35 J⋅mol−1⋅K−1\Delta S_2 = -35\,\text{J}\cdot\text{mol}^{-1}\cdot\text{K}^{-1} • Forming ion–dipole interactions: ΔH3=−805 kJ⋅mol−1\Delta H_3 = -805\,\text{kJ}\cdot\text{mol}^{-1}, ΔS3=+120 J⋅mol−1⋅K−1\Delta S_3 = +120\,\text{J}\cdot\text{mol}^{-1}\cdot\text{K}^{-1} (1) Determine the overall ΔH∘\Delta H^\circ (kJ mol⁻¹) for the dissolution of MX. (2) Determine the overall ΔS∘\Delta S^\circ (J mol⁻¹ K⁻¹) for the dissolution of MX. (3) Calculate ΔG∘\Delta G^\circ (kJ mol⁻¹) for the dissolution of MX at 298 K.

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