Finding Theoretical Yield and Percent Yield

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Finding Theoretical Yield and Percent Yield
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Theoretical Yield

• The theoretical yield is the maximum amount of
  product in grams that can be made.
• In other words its the amount of product
  possible in grams as calculated through the
  stoichiometry problem.
• This is different from the actual yield, which is
  the amount one actually produces and measures.

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Percent Yield

• One finds the percent yield by comparing the
  amount actually obtained (actual yield) to the
  amount it was possible to make (theoretical
  yield).
• Practice Problems Ch 9 27, 28, 30

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Finding Empirical Formulas
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Calculating Empirical Formulas

• One can calculate the empirical formula from the
  percent composition.

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Calculating Empirical Formulas
The compound para-aminobenzoic acid (you may have
seen it listed as PABA on your bottle of
sunscreen) is composed of carbon (61.31),
hydrogen (5.14), nitrogen (10.21), and oxygen
(23.33). Find the empirical formula of PABA.
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Calculating Empirical Formulas
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Calculating Empirical Formulas
Calculate the mole ratio by dividing by the
smallest number of moles
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Calculating Empirical Formulas
These are the subscripts for the empirical
formula C7H7NO2
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Combustion Analysis

• Compounds containing C, H and O are routinely
  analyzed through combustion in a chamber like
  this.
• C is determined from the mass of CO2 produced.
• H is determined from the mass of H2O produced.
• O is determined by difference after the C and H
  have been determined.

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Practice Problem

• Analysis of an unknown organic compound
  containing only C, H, and O shows
• A 14.3 g sample of the unknown burns to produce
  13.7 g CO2 and 11.2 g H20.
• Determine of each element in original compound.
• Determine the empirical formula for original
  compound.
• If the average molecular weight of this unknown
  compound is 138 g/mole , what is the molecular
  formula?