Percent Yield

1
Percent Yield

• Section 12.3

2
Percent Yield

• Often when reactions are actually carried out in
  the lab, there is a difference between the amount
  of product we expect and the amount we actually
  get.
• Side reactions take place that we cant control
• Impure reactants
• Loss of product due to transfers
• Errors in measuring reactants or products
• Impurities in products (ex - dirty glassware)

3
Terms

• Theoretical Yield maximum amount of product
  that could be formed from the amounts of
  reactants given
• Calculated number
• Actual Yield the actual amount of product made
  when the reaction is carried out in a lab
• Experimental number
• Percent Yield ratio of the actual yield to the
  theoretical yield expressed as a percentage
• almost always less than 100

4
Equation and Steps

• Steps
• Find theoretical yield by solving a basic
  stoichiometry problem using the amount of
  reactant given (usually 3-step problem)
• Calculate percent yield using value from 1 and
  amount of product given in the problem.

5
Example Problems

• When 84.8 g of iron(III) oxide reacts with an
  excess of carbon monoxide, 54.3 g of iron are
  produced. What is the percent yield?
• Fe2O3 3 CO ? 2 Fe 3 CO2
• Lead nitrate can be decomposed by heating. What
  is the percent yield of the decomposition
  reaction if 9.9 g Pb(NO3)2 are heated to give 5.5
  g of PbO?
• 2 Pb(NO3)2 ? 2PbO 4NO2 O2

6
Work with your partner

• In a particular reaction between copper metal and
  silver nitrate, 12.7 g Cu produced 38.1 g Ag.
  What is the percent yield of silver in this
  reaction?
• Cu 2 AgNO3 ? Cu(NO3)2 2 Ag