Ammonia Production
List THREE starting materials for the production of ammonia.
1. Methane (natural gas)
2. Steam (water vapour)
3. Air
An increase in the operating temperature resulted in a decrease in Keq. Why was this unacceptable to Haber?
When the temperature increases, the equilibrium shifts to the left (towards the reactants) to absorb the extra heat, according to Le Chatelier's Principle. This means less ammonia is formed at equilibrium, so the equilibrium constant becomes smaller.
This was unacceptable to Fritz Haber because it reduced the yield of ammonia, making the process inefficient and uneconomical for large-scale production.
However, Haber still used moderately high temperatures (~450 °C) because although the equilibrium yield decreases, the reaction rate becomes much faster, allowing ammonia to be produced quickly enough for industrial use.
State two negative environmental impacts of ammonia production or use.
Eutrophication and Soil acidification
Give ONE reason why ammonia is widely used in agriculture.
It contains a high percentage of nitrogen, which is essential for plant growth
Write ONE balanced equation for the formation of hydrogen gas, using TWO appropriate starting materials
CH4 (g) + H2O (g) -----> CO (g) + 3H2
Explain how liquefying the ammonia, as soon as it is made, affects the yield of ammonia and state the principle on which the effect is based.
When ammonia is liquefied immediately after formation, it is removed from the reaction mixture. This has two key effects:
Shifts equilibrium to the right: According to Le Chatelier's Principle, removing a product from a system at equilibrium causes the reaction to produce more product to replace what was removed. So more ammonia is formed from nitrogen and hydrogen.
Increases overall yield: Because ammonia is constantly being removed, the reaction keeps shifting toward ammonia formation, resulting in a higher total yield than if the ammonia remained as a gas in the mixture.
Describe what would be detected on a plot of land to which urea has been ap-plied during moist, warm weather.
A pungent smell
Increase soil pH
State ONE use of ammonia in the agricultural sector.
Production of fertilisers
State the conditions of BOTH pressure AND temperature needed for the formation of hydrogen gas when a nickel catalyst is used
High temperature of 700-1100 C
Moderate pressure of 20 atm
Outline TWO steps taken by Haber to increase the yield of ammonia and explain how these modifications led to the improvement in ammonia production.
Increase pressure → favors side with fewer gas molecules → more ammonia formed (Le Chatelier’s Principle)
Use a catalyst → speeds up reaction rate → ammonia forms faster without changing equilibrium
Moderate temperature → balances reaction rate and yield → avoids very low yields from high temperatures
Remove ammonia immediately (liquefaction) → shifts equilibrium right → increases overall ammonia yield (Le Chatelier’s Principle)
Recycle unreacted nitrogen and hydrogen
Urea is susceptible to the temperature and moisture in the environment and can be hydrolysed by these conditions. State the products of hydrolysis of urea.
Ammonia and Carbon dioxide
Name THREE features of ammonia gas which make it important in agriculture.
High nitrogen content
Highly soluble in water
Easily converted into fertilisers
Explain how carbon monoxide interferes with the Haber-Bosch reaction.
It poisons the iron catalyst. CO molecules strongly adsorb onto the surface of the iron catalyst, occupying the active sites where nitrogen and hydrogen are supposed to attach, preventing them from reacting.
Using Le Chatelier's principle, describe the conditions under which optimal yields o ammonia can be obtained.
Full answer on handout
Write a balanced equation for the formation of urea from ammonia.
2NH3 (g) + CO2 (g) ----> NH2CONH2 (s) + H2O (l)
State two household uses of ammonia.
Cleaning products and as a refrigerant