CAIE A Level Chemistry 9701 · Group 2
Compare the trend in thermal stability of the carbonates of the Group 2 elements from magnesium to barium with the trend in solubility of the sulfates of these elements. Explain each trend in terms of the polarising power of the cation and the relative magnitudes of the enthalpy change of hydration and the lattice energy.
5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.
Compare means: Give similarities or differences between two things, and say which side each point belongs to. Write each point as a pair, for example: A is X, whereas B is Y. Two separate descriptions rarely earn the marks.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.