AQA A Level Chemistry复习笔记1.2.5 Atom Economy

Atom Economy

 

  • The atom economy of a reaction shows how many of the atoms used in the reaction become the desired product
    • The rest of the atoms or mass is wasted

     

  • It is found directly from the balanced equation by calculating the Mr of the desired product

Atom-economy-equation

  • In addition reactions, the atom economy will always be 100%, because all of the atoms are used to make the desired product
    • Whenever there is only one product, the atom economy will always be 100%

     

  • For example, in the reaction between ethene and bromine:

CH2=CH2 + Br2 → CH2BrCH2Br

Exam Tip

Careful: sometimes a question may ask you to show your working when calculating atom economy. In this case, even if it is an addition reaction and it is obvious that the atom economy is 100%, you will still need to show your working.

  • The atom economy could also be calculated using mass, instead or Mr
  • In this case, you would divide the mass of the desired product formed by the total mass of all reactants, and then multiply by 100

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