CAIE A Level Chemistry 9701 · Group 17
Chlorine reacts with hydrogen in sunlight to form hydrogen chloride. Iodine reacts with hydrogen only when heated strongly, and the reaction is reversible.
Compare the reactions of chlorine and iodine with hydrogen, and explain the difference in reactivity in terms of the oxidising ability of the elements. Suggest why the hydrogen iodide formed is less thermally stable than hydrogen chloride.
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.