Producing Ammonia
Producing ammonia: The Haber process
Ammonia (\(\text{NH}_{3}\)) plays an important role in the manufacturing process of fertilizers. The industrial process used to produce ammonia is called the Haber process. In this reaction nitrogen gas and hydrogen gas react to produce ammonia gas. The equation for the Haber process is:
\(\text{N}_{2}(\text{g}) + 3\text{H}_{2}(\text{g})\) \(\rightleftharpoons\) \(2\text{NH}_{3}(\text{g})\)
This reaction takes place in the presence of an iron (Fe) catalyst under high pressure (\(\text{200}\) atmospheres (atm)) and temperature (\(\text{450}\) – \(\text{500}\)\(\text{°C}\)) conditions.
Fact:
\(\text{1}\) \(\text{atm}\) = \(\text{101.3}\) \(\text{kPa}\)
By the \(\text{20}\)th century, a number of methods had been developed to fix atmospheric nitrogen, in other words to make it usable for plants. Sources of nitrogen for fertilizers included saltpetre (\(\text{NaNO}_{3}\)) from Chile, and guano. Guano is the droppings of seabirds, bats and also seals. In the early \(\text{20}\)th century, before the start of the First World War, the Haber process was developed by two German chemists, Fritz Haber and Karl Bosch. They determined what the best conditions were in order to get a high yield of ammonia, and found these to be high temperature and high pressure. During World War I, the ammonia produced by the Haber process was used to make explosives.
Fact:
The forward reaction of the Haber process is exothermic, so the forward reaction is favoured by low temperatures. However, low temperatures slow all chemical reactions. So, the Haber process requires high temperatures, and the ammonia is removed as soon as it is formed to prevent it being used in the reverse reaction.
Optional Video: The chemical reaction that feeds the world
How do we grow crops quickly enough to feed the Earth's billions? It's called the Haber process, which turns the nitrogen in the air into ammonia, easily converted in soil to the nitrate plants need to survive. Though it has increased food supply worldwide, the Haber process has also taken an unforeseen toll on the environment. Daniel D. Dulek delves into the chemistry and consequences in the TED-Ed video below.
This lesson is part of:
Chemistry and the Real World