chemistry

How do you calculate the yield of a reaction

Yield of a reaction:

The quantity of product produced in a reaction is called yield of the reaction.

Types of Yield of a reaction

yield of the reaction is of three types.

(i)  Theoretical Yield  

     The quantity of product as calculated by stoichiometric calculations or calculations based on balanced equation is called theoretical yield.

(ii)   Actual Yield:

    The quantity of product that is practically obtained after the completion of reaction is called actual yield.

  • The actual yield is always less than theoretical yield due to following reasons.
  • Mechanical losses:
  • Mechanical losses may occur at different stages e.g. while handling of sample, during separation of product, during purification of product etc.
  • Side reactions: Some time due to side reactions, some of the reactants or product change to another substance and therefore amount of actual product will be less.
  • Reversibility of reaction:
  • Due to reverse reaction some of the product changes back to reactants.
  • Non-activated molecules:
  • All the molecules of reactants are not activated. Non-activated molecules (i.e. molecules possessing energy less than activation energy) will not react.
  • Impurity:
  • every sample has impurities in it. Even highly pure substance has little bit impurities. So actual yield will be less.
  • Reaction conditions: If conditions are not favorable then actual yield will be low.

So it is worth to calculate percentage yield.

(iii) Percentage Yield:

Percentage Yield   =         Actual yield x  100        

                                                           Theoretical yield      

              

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