Haber Process & NPK Fertilisers (AQA GCSE Chemistry)

The temperature and pressure used in the Haber process is 450^oC and 200 atmospheres.

As temperature increases, the yield of ammonia decreases.

The temperature and pressure which produce the maximum yield of ammonia is 350^oC and 400 atmospheres.

True.

The conditions for the Haber process are chosen based on cost, yield, rate and availability of raw materials.

Compromise conditions are the conditions chosen to give a good balance between product yield, reaction rate and production cost, rather than ideal conditions for any one factor.

A temperature of 450^oC is chosen because a higher temperature would favour the reverse reaction as its endothermic and a lower yield of ammonia would be made. A lower temperature would reduce the rate of reaction.

A compromise pressure of 200 atm is used because higher pressures would be dangerous and expensive equipment is needed but lower pressures would cause the reverse reaction of be favoured and a lower yield of ammonia would be made.

True.

Catalysts do not change the position of equilibrium.

False.

A catalyst speeds up the rate of both the forward and backward reactions.

It is not desirable to use high pressures in industrial processes because very expensive equipment is needed and it can be dangerous.

A fertiliser is a compound containing nutrients that is applied to soil or plants to promote growth and increase crop yields.

The three essential elements in fertilisers are nitrogen, phosphorus, and potassium.

The ammonium ion is NH₄⁺.

Nitrate ions (NO₃^-) are a source of soluble nitrogen in fertilisers.

The formula of the phosphate ion is PO₄^3-.

False.

Most common potassium compounds dissolve in water to produce potassium ions (K⁺), which are a component of fertilisers.

The balanced symbol equation is:

NH₃ (aq) + HNO₃ (aq) → NH₄NO₃ (aq)

Plants require nitrogen, potassium and phosphorus because:

• Nitrogen promotes healthy leaves,

• Potassium promotes growth, healthy fruit and flowers

• Phosphorus promotes healthy roots

The Haber process produces ammonia industrially.

Sulfuric acid is sprayed into a chamber of ammonia gas to form ammonium sulfate.

The laboratory method used to produce ammonium sulfate is a titration.

True.

NPK fertilisers are an example of a formulation because they are a mixture designed as a useful product.

The products formed when phosphate rock is treated with sulfuric acid are calcium sulfate and calcium phosphate. The mixture is known as single superphosphate.

The products formed when phosphate rock is treated with nitric acid are phosphoric acid and calcium nitrate.

The product formed when phosphate rock is treated with phosphoric acid is calcium phosphate, also known as triple superphosphate.

Phosphate rock needs to be reacted with acids as the phosphate salts in the rock are insoluble so won't be absorb by plants. Adding acids to them produces soluble phosphates.

False.

Making ammonium sulfate in a lab is slower than making it on an industrial scale.