CAIE A Level Chemistry 9701 · Group 2
Explain why the thermal stability of Group 2 carbonates increases down the group, and why the solubility of Group 2 sulfates decreases down the group. In your answer, refer to the polarising power of the cation and the relative magnitudes of lattice energy and hydration enthalpy.
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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