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Edexcel IAL Chemistry 12.14 Experimental and theoretical lattice energy

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

Syllabus
First assessment 2019
Course
Chemistry YCH11
Level
A2

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.

12.19—Entropy and enthalpy changes of solution values to predict the solubility of ionic compounds and discuss trends in question 1

[Maximum number: 1]

The standard enthalpy change of solution of potassium chloride， KCl ，is +17 kJ mol−1+17 \mathrm{~kJ} \mathrm{~mol}^{-1} ．
The solubility of potassium chloride in water at 298 K is 359gdm−3359 \mathrm{gdm}^{-3} ．
Which of these explains the solubility of potassium chloride in water？

A

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

B

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

C

the total entropy change when KCl dissolves is positive

D

the total entropy change when KCl dissolves is negative

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