Eduqas GCSE Chemistry 11 Production, Use and Disposal of Important Chemicals and Materials Exam Questions

About Eduqas GCSE Chemistry 11 Production, Use and Disposal of Important Chemicals and Materials

This Eduqas GCSE Chemistry topic applies earlier chemistry to industry and sustainability. You study the Haber process and the compromise conditions chosen, how ammonia is used to make NPK fertilisers, and how to calculate percentage yield and atom economy. It also covers rusting and how to prevent it, alloys such as steel and brass, choosing materials from their properties, life cycle assessments and recycling. SP11 measures the percentage of water in a hydrated salt. The topic draws on equilibrium (topic 9), moles (topic 3) and metals (topic 6). Examiners often ask you to justify the Haber process conditions, calculate yield or atom economy, and evaluate a life cycle assessment.

What you need to know

• Haber process N2 + 3H2 ⇌ 2NH3, forward reaction exothermic. Typical conditions: about 450 °C, about 200 atmospheres and an iron catalyst. A lower temperature would give a higher yield but too slow a rate; higher pressure would increase yield but costs more and is less safe. Unreacted gases are recycled.
• Fertilisers NPK fertilisers supply nitrogen, phosphorus and potassium for plant growth. Ammonia is used to make nitric acid and ammonium salts such as ammonium nitrate and ammonium sulfate.
• Yield and atom economy Percentage yield = (actual mass / theoretical mass) x 100. Atom economy = (Mr of desired product / total Mr of reactants) x 100. A high atom economy means less waste and is more sustainable.
• Corrosion Rusting needs both water and oxygen. It is prevented by barriers (paint, oil, plastic), galvanising with zinc, or sacrificial protection, where a more reactive metal corrodes instead of the iron.
• Alloys and materials Alloys are harder than pure metals because different sized atoms disrupt the layers so they cannot slide. Steel, brass and bronze are common alloys. Materials are chosen by properties such as strength, density, conductivity and cost.
• Life cycle assessment and SP11 A life cycle assessment considers raw materials, manufacture, use and disposal. Reduce, reuse and recycle conserves resources and energy. SP11: heat a hydrated salt such as copper(II) sulfate to constant mass to find the percentage of water.

Common mistakes in 11 Production, Use and Disposal of Important Chemicals and Materials

• Saying 450 °C is used because it gives the highest yield. It is a compromise between an acceptable yield and a fast enough rate.
• Confusing percentage yield with atom economy. Yield compares actual and theoretical product; atom economy compares the mass of desired product with all products from the equation.
• Saying galvanising works only as a barrier. Zinc is also more reactive than iron, so it corrodes sacrificially even if scratched.
• Stating that alloys are harder because they are stronger metals. Explain that different sized atoms distort the layers so they cannot slide.
• Heating a hydrated salt once only. Heat to constant mass so that all the water has been removed.

Try three 11 Production, Use and Disposal of Important Chemicals and Materials exam-style questions