Chapter 9 Lecture

Basic ChemistryFourth Edition

9.4 Percent Yield

Learning Goal Given the actual quantity of product, determine the percent yield for a reaction.

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Chapter 9 Chemical Quantities in Reactions

Theoretical yield is the amount of product we expect, if all the reactants were converted to the desired product.

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

Percent yield is the ratio of actual yield to theoretical yield.

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Percent Yield

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On a space shuttle, LiOH is used to absorb exhaled CO2 and form LiHCO3.

LiOH(s) + CO2(g) LiHCO3(s)

Calculating Percent Yield

On a space shuttle, the LiOH in the canisters removes Co2 from the air.

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Calculating Percent Yield

What is the percent yield of LiHCO3 if 50.0 g of LiOH produces 72.8 g of LiHCO3?

LiOH(s) + CO2(g) LiHCO3(s)

Step 1 State the given and needed quantities. Given: 50.0 g of LiOH,

72.8 g of LiHCO3

Need: Theoretical yield, LiHCO3 Percent yield, LiHCO3

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LiOH(s) + CO2(g) LiHCO3(s)

50.0 g 72.8 g Actual yield? Theoretical yield

Step 2 Write a plan to calculate the theoretical and percent yield.

Calculating Percent Yield

grams of LiOH

Molar MassMolar Mass

moles ofLiOH

Molar MassMolar Mass

moles of LiHCO3

grams ofLiHCO3

Mole–Mole factor

Mole–Mole factor

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LiOH(s) + CO2(g) LiHCO3(s)

50.0 g 72.8 g Actual yield? Theoretical yield

Step 3 Write the molar mass and mole−mole factors.

1 mole of LiOH = 23.95 g of LiOH

Calculating Percent Yield

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LiOH(s) + CO2(g) LiHCO3(s)

50.0 g 72.8 g Actual yield? Theoretical yield

Step 3 Write the molar mass and mole−mole factors.

1 mole of LiHCO3 = 67.96 g of LiHCO3

Calculating Percent Yield

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LiOH(s) + CO2(g) LiHCO3(s)

50.0 g 72.8 g Actual yield ? Theoretical yield

Step 3 Write the molar mass and mole−mole factors.

1 mole of LiOH = 1 mole of LiHCO3

Calculating Percent Yield

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Calculating Percent Yield

LiOH(s) + CO2(g) LiHCO3(s)

50.0 g 72.8 g Actual yield? Theoretical yield

Step 4 Calculate the percent yield by dividing the actual yield by the theoretical yield and multiplying by 100%. Calculation of theoretical yield:

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Calculating Percent Yield

LiOH(s) + CO2(g) LiHCO3(s)

50.0 g 72.8 g Actual yield ? Theoretical yield

Step 4 Calculate the percent yield by dividing the actual yield by the theoretical yield and multiplying by 100%. Calculation of theoretical yield:

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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 of CO is produced when 30.0 g of O2 is used?

Learning Check

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What is the percent yield if 40.0 g of CO is produced when 30.0 g of O2 is used?2C(g) + O2(g) 2CO(g)

30.0 g 40.0 g Actual yield ? Theoretical yield

Step 1 Write the given and needed quantities. Given: 30.0 g of O2, 40.0 g of CO Need: Theoretical yield, CO

Percent yield, CO

Solution

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2C(g) + O2(g) 2CO(g) 30.0 g 40.0 g Actual yield

? Theoretical yield

Step 2 Write a plan to calculate the theoretical and percent yield.

Solution

grams of O2

Molar MassMolar Mass

moles of O2

Molar MassMolar Mass

moles of CO

grams of CO

Mole–Mole factor

Mole–Mole factor

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2C(g) + O2(g) 2CO(g) 30.0 g 40.0 g Actual yield

? Theoretical yield

Step 3 Write the molar mass and mole–mole factors. 1 mole of O2 = 32.00 g of O2

Solution

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2C(g) + O2(g) 2CO(g) 30.0 g 40.0 g Actual yield

? Theoretical yield

Step 3 Write the molar mass and mole–mole factors.

1 mole of CO = 28.01 g of CO

Solution

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2C(g) + O2(g) 2CO(g) 30.0 g 40.0 g Actual yield

? Theoretical yield

Step 3 Write the molar mass and mole–mole factors. 1 mole of O2 = 2 moles of CO

Solution

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2C(g) + O2(g) 2CO(g) 30.0 g 40.0 g Actual yield

? Theoretical yield

Step 4 Calculate the percent yield by dividing the actual yield by the theoretical yield and multiplying by 100%. Calculation of theoretical yield:

Solution

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2C(g) + O2(g) 2CO(g) 30.0 g 40.0 g Actual yield

? Theoretical yield

Step 4 Calculate the percent yield by dividing the actual yield by the theoretical yield and multiplying by 100%. Calculation of theoretical yield:

Solution