HSC Chemistry
9.4 Chemical Monitoring and Management
Section 2 Haber Process
2002
2003
2005
2006
2008
Question 23 (4 marks)
Using Le Chatelier’s principle, justify the choice of temperature and pressure
conditions used to optimise the yield in the Haber process.
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Question 23
The better responses included a balanced equation including states, reversible arrows and the negative
ΔH. They also identified that the reaction was exothermic as well as identifying the conditions for
temperature and pressure used. The better responses explained why the temperature and pressure
values are used. The better responses explained the link between pressure and Le Chatelier’s Principle
using the moles ratio in gaseous terms as well as temperature and Le Chatelier’s Principle (including
rate of reaction as well as yield). The weaker responses referred to pressure as a reactant. Weaker
responses included a detailed account of the Haber process but did not answer the question.
2010
9 What types of reaction occur in the Haber process during the production of ammonia?
(A) Redox and synthesis
(B) Hydration and redox
(C) Decomposition and oxidation
(D) Reduction and decomposition
2012
Sample answer:
Ammonia is important as it is used extensively in many industries. It is a raw material in
agriculture for the making of fertilisers to increase crop production. It is used to produce
explosives for wartime or construction and mining. Its importance can further be seen in its
use in manufacturing synthetic fibres, cleaning products and pharmaceuticals.
Question 24
In better responses, candidates effectively linked the properties of ammonia with its uses in
industry.
In weaker responses, candidates tended to include information about the historical development of
the Haber process as a means of producing ammonia, rather than explaining its current industrial
uses. In these responses, candidates stated several uses of ammonia, but did not explain why these
uses were important.