OCR GCSE Chemistry A C6.1 Improving Processes and Products Exam Questions

About OCR GCSE Chemistry A C6.1 Improving Processes and Products

C6.1 applies chemistry to real industrial processes and products. On the OCR Gateway Chemistry A course it opens Topic C6 Global challenges, assessed in Paper 2 (Foundation) or Paper 4 (Higher). You study how metals are extracted, how ammonia and fertilisers are produced, how the environmental impact of products is assessed, and how materials such as alloys are used and protected from corrosion. It draws together redox and electrolysis from C3, reactivity from C4.1, and rates and equilibria from C5. Examiners often test choice of extraction method, the compromise conditions in the Haber process, life cycle assessment evaluations and reacting mass calculations for extraction.

What you need to know

• Extraction with carbon Metals less reactive than carbon, such as iron and zinc, are extracted by reduction of their oxides with carbon. For example, 2Fe2O3 + 3C -> 4Fe + 3CO2.
• Extraction by electrolysis Metals more reactive than carbon, such as aluminium, are extracted by electrolysis of the molten compound. Aluminium oxide is dissolved in molten cryolite to lower the operating temperature; aluminium forms at the cathode and oxygen at the anode, which burns the carbon anodes away.
• Biological methods Phytoextraction uses plants to absorb metal compounds from soil; the plants are burned and the ash processed. Bacterial extraction (bioleaching) uses bacteria to produce solutions containing metal compounds. Both are useful for low-grade ores.
• The Haber process and fertilisers Ammonia is made from nitrogen and hydrogen at about 450 degrees C, 200 atmospheres and with an iron catalyst; these are compromise conditions balancing yield, rate and cost. Ammonia is used to make NPK fertilisers such as ammonium nitrate and ammonium sulfate.
• Life cycle assessment and recycling A life cycle assessment considers the environmental impact of a product from extracting raw materials, through manufacture and use, to disposal. Recycling saves raw materials and energy and reduces waste, though collection and sorting have costs.
• Corrosion and alloys Rusting needs both water and oxygen. It is prevented by barriers such as paint, oil or plastic, or by sacrificial protection with a more reactive metal such as zinc (galvanising). Alloys such as steel, brass and bronze are harder than pure metals because different sized atoms stop layers sliding.

Common mistakes in C6.1 Improving Processes and Products

• Saying aluminium is extracted with carbon. Aluminium is more reactive than carbon, so it must be extracted by electrolysis.
• Stating that cryolite is a catalyst. It is used as a solvent to lower the melting point and save energy.
• Explaining Haber conditions only in terms of yield. A lower temperature gives a higher yield but too slow a rate, so 450 degrees C is a compromise.
• Writing that galvanising works only as a barrier. Zinc also corrodes in preference to iron (sacrificial protection) even if scratched.
• Treating a life cycle assessment as fully objective. Some stages, such as pollution effects, require value judgements.

Try three C6.1 Improving Processes and Products exam-style questions