Percent Yield - PowerPoint PPT Presentation

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Percent Yield

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Percent Yield Section 12.3 Percent Yield Often when reactions are actually carried out in the lab, there is a difference between the amount of product we expect and ... – PowerPoint PPT presentation

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Title: 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
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