CAIE A Level Chemistry 9701 · Nitrogen and sulfur
When welding reactive metals such as titanium, the metal is often heated in an atmosphere of nitrogen rather than air. Using your knowledge of the chemistry of nitrogen and ammonia, describe and explain:
(a) why nitrogen gas is unreactive, even at the high temperatures used in welding, (b) how ammonia can be formed from nitrogen and how it behaves as a Brønsted–Lowry base when it reacts with hydrogen chloride, (c) how ammonia can be displaced from ammonium 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.
Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.