AQA GCSE Chemistry

Revision Notes

3.3.4 Choosing a Reaction Pathway

Higher Tier Only

Choosing a Reaction Pathway

  • Reactions that have low atom economies use up a lot of resources and produce a lot of waste material which then needs to be disposed of, a very expensive procedure
  • These reactions are thus unsustainable as they use up too much raw material to manufacture only a small amount of product
  • They are not economically attractive as raw materials tend to be expensive, as does waste disposal which requires chemicals, equipment, space and transport
  • Companies continually analyse reactions and processes and evaluate several factors in an effort to improve efficiency
  • Atom economy, percentage yield, rates of reaction and equilibrium position are important factors which need to be considered when choosing a reaction pathway
  • High percentage yields and fast reaction rates are desirable attributes in industrial chemical processes
  • In reversible reactions, the position of the equilibrium may need to be changed in favour of the products by altering reaction conditions
  • If the waste products can be sold or reused in some way that would improve the atom economy
  • Alternative methods of production could also be considered that may produce a more useful by-product

Exam Tip

Look for information on percentage yield, atom economy, rate and equilibria in questions on this topic. Your answer should then be based on evaluating (for example by comparing the pros and cons of) this information.

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.

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