Calculating Atom Economy (AQA GCSE Chemistry)

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Calculating Atom Economy

  • Along with the percentage yield, atom economy is used to analyse the efficiency of reactions
  • Most reactions produce more than one product and very often some of them are not useful
  • Atom economy studies the amount of reactants that get turned into useful products
  • It illustrates what percentage of the mass of reactants become useful products
  • It is used extensively in the analysis of systems and procedures in industries, in an effort to obtain sustainable development
  • It is also a very important analysis for economic reasons as companies prefer to use processes with higher atom economies
  • The higher the atom economy of a process then the more sustainable that process is
  • The equation for calculating atom economy is:

Worked example

Hydrogen gas is obtained from methane in a process called steam-methane reforming. The reaction is as follows:

CH4 (g) + H2O (g) → CO (g) + 3H2 (g)

Calculate the atom economy of this reaction.

Answer:

Atom Economy WE, downloadable IGCSE & GCSE Chemistry revision notes

Exam Tip

Unwanted byproducts can sometimes be put to use so although a low atom economy is a sign that a process is not green (sustainable) it doesn’t necessarily imply that the process is not economically viable.

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Stewart

Author: Stewart

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.