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Ammonia

The Haber process is used in the manufacture of ammonia from nitrogen gas and hydrogen gas.N2(g) + 3H2(g) ⇌ 2NH3 (g) ΔH = -92kJmol-1Using Le Chatelier's principle, the best conditions for a high yield are a low temperature and high pressure. Both will push the equilibrium to the right.A compromise temperature of 350 - 500°C is used so the reaction proceeds at an appreciable rate and a pressure of 100-200atm is used. An iron catalyst is used to speed up the reaction. The yield is about 15% and the gases are recycled.

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Specification: AQA Chemistry (7404), AS-level, 3.1.6.1 Chemical equilibria and Le Chatelier's principle. Topic: Equilibria.

Key terms in this lesson

Catalyst
A substance that increases the rate of a chemical reaction without being used up, by providing an alternative reaction pathway with a lower activation energy.
Le Chatelier's principle
The principle that when a system at equilibrium is subjected to a change, the system readjusts to minimise the effect of that change.

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