CAIE A Level Chemistry 9701 · Group 2
The enthalpy change of solution, , of strontium hydroxide is more exothermic than that of barium hydroxide. Yet strontium hydroxide is less soluble in water at the same temperature.
Explain, in terms of the relative magnitudes of the enthalpy change of hydration and the lattice energy, why strontium hydroxide is less soluble than barium hydroxide.
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.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.