AS and A2 Chemistry notes and resources (WJEC specification) - UNIT CH5 Physical and inorganic chemistry

This unit develops ideas of redox, kinetics, energy changes and equilibria. The inorganic chemistry of some elements in various sections of the Periodic Table is studied.

19.1 - Enthalpy changes for solids and solutions

Candidates should be able to:

(a) understand the use of the terms enthalpy change of atomisation, lattice formation and breaking, hydration and solution (formal definitions are not required);

(b) explain how enthalpy changes of solution are related to lattice breaking enthalpies and hydration enthalpies of the ions;

(c) show understanding of the way in which the solubilities of ionic solids in water depend upon the balance between the lattice breaking enthalpies and the hydration enthalpies of the ions;

(d) apply Hess's Law (Born-Haber cycle) to the formation of simple ionic compounds and carry out appropriate calculations (data will be supplied as necessary);

(e) appreciate that the exothermicity or endothermicity of . . o f H may be used as a qualitative indication of the stability of the compound in question and recognise that the most stable ionic compounds will be those formed most exothermically from their elements.