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Percent Yield

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 the amount we actually get. Side reactions take place that we can’t control Impure reactants

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Percent Yield

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  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 can’t 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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