Edexcel A-Level Chemistry A2 12.19 Entropy and Enthalpy Changes of Solution Values to Predict the Solubility of Ionic Compounds and Discuss Trends in Questions

Compare magnitudes rather than signs alone: a larger experimental–theoretical difference indicates greater departure from the ideal point-ion model and more covalency.

Exam points

Calculate or compare lattice-energy differences to rank covalent character.
State theoretical assumptions such as spherical point ions, full charge and purely ionic bonding.
Link close agreement to predominantly ionic bonding and a large difference to covalency.

[Maximum number: 1]

The standard enthalpy change of solution of potassium chloride， KCl ，is $+17 \mathrm{~kJ} \mathrm{~mol}^{-1}$ ．
The solubility of potassium chloride in water at 298 K is $359 \mathrm{gdm}^{-3}$ ．
Which of these explains the solubility of potassium chloride in water？

the hydration enthalpy of $\mathrm{K}^{+}$ and the lattice energy of KCl are exothermic

the hydration enthalpy of $\mathrm{K}^{+}$ and the lattice energy of KCl are endothermic

the total entropy change when KCl dissolves is positive

the total entropy change when KCl dissolves is negative

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Edexcel A-Level Chemistry A2 12.19 Entropy and Enthalpy Changes of Solution Values to Predict the Solubility of Ionic Compounds and Discuss Trends in Questions question 1