Atom Economy

Specification Point 5.13C:
  • Recall the atom economy of a reaction forming a desired product.
  • Along with the percentage yield, atom economy is used to analyse the efficiency of reactions.
  • 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 economical 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.

Calculating Atom Economy

Specification Point 5.14C:
  • Calculate the atom economy of a reaction forming a desired product.

Equation:

Atom economy   =   (total Mr of desired product  ÷ total Mr of all products) x 100

Example:

Hydrogen gas is obtained from methane in a process called steam-methane reforming. Calculate the atom economy of this reaction.

Equation Of Reaction:    

CH4 (g)    +    H2O (g)     →     CO (g)    + 3H2 (g)

Step 1  Calculate the total Mr of all the products:

Total Mr = 28 (CO:12 + 16) + (3H2: 6 x 1) = 34

Step 2  Calculate the Mr of the desired products:

Mr of 3H2 (6 x 1) = 6

Step 3  Calculate the atom economy:

Atom economy = (6 ÷ 34) x 100 = 17.6%

Therefore in this process 82% by mass of reactants is wasted.

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Morgan Curtin Chemistry

Author: Morgan

Morgan’s passion for the Periodic Table begun on his 10th birthday when he received his first Chemistry set. After studying the subject at university he went on to become a fully fledged Chemistry teacher, and now works in an international school in Madrid! In his spare time he helps create our fantastic resources to help you ace your exams.