CAIE A Level Chemistry 9701 · Chemical energetics

Chemical energetics: explain question

Explain4 marksStandard

The lattice energy of magnesium oxide is $-3791\text{ kJ mol}^{-1}$ and that of sodium chloride is $-787\text{ kJ mol}^{-1}$ .

Define the term lattice energy and explain, in qualitative terms, why the lattice energy of magnesium oxide is more exothermic than that of sodium chloride.

How this question is marked

4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.

Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.

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