CAIE A Level Chemistry 9701 · Group 2
The thermal stabilities of the carbonates of the Group 2 elements decrease down the group. Compare the thermal stabilities of the carbonates of magnesium, calcium and barium, and explain the trend in terms of the changes in the cations. Include equations for the thermal decomposition of magnesium carbonate and calcium carbonate.
6 marks, so the mark scheme is looking for about 6 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.