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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