AQA GCSE Chemistry

Revision Notes

3.3.3 Calculating Atom Economy

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.


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.

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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