Calculating theoretical and percent yield

 

You learned how to calculate theoretical yield and percent yield in general chemistry lab. Since chemistry is a cumulative discipline, we expect students to remember topics from previous chemistry course.  Anyway, here is a brief recap:

  1. write the balanced chemical equation of the reaction

  2. if there is more than one product, determine which one (or ones) are the products of interest.  If one of the products is organic and the other is inorganic, in an organic chemistry synthesis the product of interest will be the organic compound (duh...).  If you are not certain which is the desired product, read the introduction to the procedure again.

  3. determine the moles of each reactant you will use using literature physical constants (i.e. density, MW). This includes any inorganic reactants, but not any catalysts used or reaction solvents.

  4. determine which reactant is the limiting reagent

  5. determine the moles of product expected using the balanced equation of reaction and the moles of limiting reagent.   This is the theoretical yield, expressed in moles.  This can also be expressed in units of mass using the literature MW of the product.

  6. use the mass of product obtained to determine the percent yield:

    7. percent yield =     grams of product obtained    X 100%
                                 theoretical yield (in grams)

or convert the mass of product obtained to  the moles of products obtained (using the MW of the product) to determine the percent yield:

percent yield = moles of product obtained       X 100%
                       theoretical yield (in moles)