AQA GCSE Chemistry: Using Resources

A company is carrying out a life cycle assessment (LCA) to compare a plastic (polymer) carrier bag with a paper carrier bag, to decide which has the lower environmental impact.

Describe the stages that a life cycle assessment should consider, and discuss why it can be difficult to decide which bag is better for the environment. (6 marks)

Ammonia from the Haber process is used to make NPK fertilisers, which supply plants with essential elements.

(a) State what the letters N, P and K stand for in an NPK fertiliser. (1 mark)

(b) Ammonia ($NH_3$NH3​) can be reacted with nitric acid to make the salt ammonium nitrate, a nitrogen-rich fertiliser. Write a balanced symbol equation for the reaction of ammonia with nitric acid ($HNO_3$HNO3​) to make ammonium nitrate ($NH_4NO_3$NH4​NO3​). (2 marks)

(c) Ammonia can also be neutralised by sulfuric acid to make a different nitrogen fertiliser. Name the salt produced when ammonia reacts with sulfuric acid. (1 mark)

Iron objects rust when exposed to the environment. One way of protecting iron is galvanising — coating it with a layer of zinc.

(a) State the two substances that must both be present for iron to rust. (1 mark)

(b) Explain why galvanising still protects the iron from rusting even if the zinc layer is scratched and the iron beneath is exposed. (2 marks)

Potable water is water that is safe to drink. In the UK, potable water is usually produced from fresh water (rivers and reservoirs).

(a) Explain the difference between potable water and pure water (in the chemical sense). (2 marks)

(b) Name the stage of water treatment that kills microorganisms, and name one substance or method used to do this. (1 mark)

Sulfuric acid is made industrially by the contact process. One key step is the reversible reaction in which sulfur dioxide reacts with oxygen to form sulfur trioxide:

$2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)$2SO2​(g)+O2​(g)⇌2SO3​(g)

Name the catalyst used in this step of the contact process. (1 mark) ... and state one reason a catalyst is used. (1 mark)

Metal ores are a finite resource. Recycling metals helps to conserve these resources.

State one other advantage of recycling metals, apart from conserving finite ore resources. (1 mark)