Do Now

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Read the balanced equation below and write all possible mole ratios.

2Al2O3 → 4Al(s) + 3O2(g)

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Chapter 9 Percentage Yield

Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

Essential Question

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What is the difference between the theoretical yield and the actual yield?

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Theoretical, Actual, and Percent Yield

T heoretical yield • The maximum amount of product calculated using the balanced

equation. (mass of product that should be produced from the limiting reactant)

Actual yield • The amount of product obtained when the reaction takes place.

(mass of product actually produced from the limiting reactant)Percent yield • The ratio of actual yield to theoretical yield.

percent yield = actual yield (g) x 100 theoretical yield (g)

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To calculate the percent yield, the actual yield and theoretical yield are needed.You prepared cookie dough using a recipe to make 5 dozen cookies. After all of the preparation, you only end up with 48 cookies. What is the percent yield of cookies?Theoretical yield 60 cookies possibleActual yield 48 cookies to eatPercent yield 48 cookies x 100 = 80% yield

60 cookies What are some possible sources of error?

Calculating Percent Yield

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Learning Check

Without proper ventilation and limited oxygen, the reaction of carbon and oxygen produces carbon monoxide.2C(g) + O2(g) 2CO(g)

What is the percent yield if 40.0 g CO are produced when 30.0 g O2 are used?

1) 25.0%

2) 75.0%

3) 76.2%

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Solution

3) 76.2 % yieldtheoretical yield of CO30.0 g O2 x 1 mol O2 x 2 mol CO x 28.01 g CO

32.00 g O2 1 mol O2 1 mol CO= 52.5 g CO (theoretical)

percent yield 40.0 g CO (actual) x 100 = 76.2 % yield

52.5 g CO (theoretical)

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Learning CheckWhen N2 and 5.00 g H2 are mixed, the reaction produces 16.0 g NH3. What is the percent yieldfor the reaction?N2(g) + 3H2(g) 2NH3(g)

1) 31.3 %2) 56.5 %3) 80.0 %

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Solution

2) 56.5 %N2(g) + 3H2(g) 2NH3(g)

5.00 g H2 x 1 mol H2 x 2 mol NH3 x 17.03 g NH3

2.016 g H2 3 mol H2 1 mol NH3

= 28.2 g NH3 (theoretical)

Percent yield = 16.0 g NH3 x 100 = 56.7 %

28.2 g NH3