Percent Yield 12.5

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					                                    Percent Yield
• Procedure when calculating the number of grams of product from a certain number of
    grams of reactant:

•   2KClO3               2KCl + 3O2

• How many grams of O2 can be produced from 50 grams of KClO3?
•Procedure when calculating the number of grams of product from a certain number of
grams of reactant:
•2KClO3              2KCl + 3O2
•How many grams of O2 can be produced from 50 grams of KClO3?
•

Step 1 – Convert the grams of known compound to moles by dividing by its molar mass.
50 g KClO3
                      = 0.47 mol KClO3
106 g/mol KClO3

Step 2 – Multiply the number of moles by the mole ratio of unknown to known from the
coefficients of the balanced equation.
0.47 mol KClO3         3 mol O2
                   X                 = 0.71 mol O2
                     2 mol KClO3


Step 3 – Multiply the number of moles times the molar mass of the product (answer).
0.71 mol O2            32 g O2
               X                  = 22.6 g O2
                     1 mol O2
• When an experiment is carried out, the maximum amount of product possible
  (theoretical yield) is not usually obtained.
• The actual amount of product obtained is called the actual yield.
• The theoretical yield is calculated through a stoichiometry calculation.

•   The percent yield is the percent of actual yield based on the theoretical yield.
•   % yield = (actual yield/theoretical yield) X 100
•   In the above example, suppose only 15 grams of O2 is obtained.
•   The percent yield = (15/22.6) X 100 = 66.4%

				
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posted:5/28/2011
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