CALCULATIONS
The balanced equation for n-butyl acetate synthesis [equation 2] shows that the reaction requires the same
number of moles of acetic acid as of n-butyl alcohol. Thus, complete conversion of the starting materials to product
requires equimolar amounts of acid and alcohol. What would happen if the amounts taken for a particular reaction
were not equal? Even if the equilibrium were somehow pushed as far as possible in the direction of the products,
part of the reactant present in excess would have no choice but to remain left over and unchanged.
Clearly the reactant present in smaller molar amount (either acid or alcohol) limits the maximum amount of
product that can be formed (the “theoretical yield”). This limiting reactant becomes the basis for calculating the
percent yield
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obtained in your experiment. If the number of moles of butyl acetate formed comes out to be equal to
the number of moles of limiting reactant, the yield is as high as it possibly could be and the percent yield is 100%.
Put differently, a 100% yield corresponds to a number of moles of ester product equal to the number of moles of
whichever reactant was present in short supply. Actual product yields are reported as the percentage of the number of
moles of the limiting reactant. If you started with 0.33 mole of acetic acid and 0.50 mole of butanol, your limiting
reactant would be acetic acid. If, from such a reaction, you isolated 0.22 mole of butyl acetate (i.e., your reaction
yielded 0.22 mole of product), your percent yield would be