Theoretical Yield

and Percent YieldHOW MUCH DID YOU ACTUALLY GET?

Theoretical Yield

� Use chemical reactions to tell us what SHOULD happen in a reaction

� Mg(OH)2 + 2 HCl � MgCl2 + 2 H2O

� 50.6 g sample of Mg(OH)2 is reacted with HCl. How many grams of H2O will we create?

� 50.6g Mg(OH)2 1 mol Mg(OH)2 2 mol H2O 18.02 g H2O = 31.26g

58.33g Mg(OH)2 1 mol Mg(OH)2 1 mol H2O H2O

� 31.26g is the Theoretical Yield of H2O

� This is just a Mass to Mass conversion

Percent Yield

�Percent Yield – a ratio relating the

efficiency of a chemical reaction

� Percent Yield = Actual Yield x 100

Theoretical Yield

Percent Yield

� Actual Yield – What you actually got from

the reaction/experiment

� Theoretical Yield – What you expected to

get from the reaction/experiment

� Your ACTUAL YIELD should always be LESS

than your THEORETICAL YIELD

� Nothing is PERFECT!

Percent Yield

� The Theoretical Yield of H2O was 31.26g.

� If we only actually make 28.42g of H2O, what is the

Percent Yield of H2O?

� Percent Yield = Actual Yield x 100

Theoretical Yield

� 28.42g H2O x 100 = 90.9% Yield

31.26g H2O

Theoretical and Percent Yield

� According to the reaction:

� SiO2 + 3 C � SiC + 2 CO

� A student uses 37.9g of SiO2 to complete the reaction.

What is the theoretical yield of CO in grams?

� 37.9g SiO2 1 mol SiO2 2 mol CO 28.01 g CO =

60.09g SiO2 1 mol SiO2 1 mol CO

� 35.33 g CO

Theoretical and Percent Yield

� If the student only managed to create 24.90g

of CO in the lab, what is the percent yield?

� Theoretical Yield = 35.33 g CO

�Actual Yield = 24.90 g CO

�Percent Yield = 24.90 g CO x 100 = 70.48%

35.33 g CO

Theoretical and Percent Yield

�According to the reaction:

� Al2O3 + 3C � 2Al + 3CO

�A student begins the reaction with 59.2g of

Al2O3 and 38.6g of Carbon. If the student

only managed to create 27.41g of Al, what

is the percent yield?

� First, we have to find which reactant is Limiting

Reactant and then calculate a Theoretical Yield

Theoretical and Percent Yield

� Al2O3 + 3C � 2Al + 3CO

� A student begins the reaction with 59.2g of Al2O3 and 38.6g of Carbon. If the student only managed to create 27.41g of Al, what is the percent yield?

� 59.2g Al2O3 1 mol Al2O3 2 mol Al 26.98g Al = 31.33g

101.96g Al2O3 1 mol Al2O3 1 mol Al Al

� 38.6g C 1 mol C 2 mol Al 26.98g Al = 57.81g Al

12.01g C 3 mol C 1 mol Al

� Limiting Reactant is Al2O3� Theoretical Yield of Al is 31.33g

Theoretical and Percent Yield

�Theoretical Yield of Al is 31.33g

�Actual Yield is 27.41g

�Percent Yield = 27.41 g Al x 100 = 87.5%

31.33 g Al

Theoretical and Percent Yield

� 2 H2 + CO � CH3OH

� If you react 47.2L of CO with 19.7L of H2, what is the Theoretical Yield of CH3OH in grams?

� Find Limiting Reactant in grams

� 47.2L CO 1 mol CO 1 mol CH3OH 32.02g CH3OH =

22.4L CO 1 mol CO 1 mol CH3OH

� 67.47g CH3OH

� 19.7L H2 1 mol H2 1 mol CH3OH 32.02g CH3OH =

22.4L H2 2 mol H2 1 mol CH3OH

� 14.08g CH3OH

� Limiting Reactant is H2� Theoretical Yield is 14.08g CH3OH

Theoretical and Percent Yield

� Theoretical Yield is 14.08g CH3OH

� If we actually made 10.14g of CH3OH, what is

our Percent Yield?

� 10.14g CH3OH x 100 = 72.01%

14.08g CH3OH