Limiting Reactants (Reagents)
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Limiting Reactants (Reagents) and Percent Yield
description
Limiting Reactants (Reagents). and Percent Yield. Calculations need to be based on the limiting reactant. Example 1: Suppose a box contains 87 bolts, 110 washers and 99 nails. How many sets of 1 bolt, 2 washers and 1 nail can you use to create? What is the limiting factor? - PowerPoint PPT Presentation
Transcript of Limiting Reactants (Reagents)
Limiting Reactants (Reagents)
and Percent Yield
Calculations need to be based on the limiting reactant.
• Example 1: Suppose a box contains 87 bolts, 110 washers and 99 nails. How many sets of 1 bolt, 2 washers and 1 nail can you use to create? What is the limiting factor?
55 sets; washers limit the amount
Calculations need to be based on the limiting reactant.
• Example 2: What is the maximum mass of sulfur dioxide that can be produced by the reaction of 95.6 g carbon disulfide with 100. g oxygen?CS2 + O2 CO2 + SO2
Start by balancing the equation…
Calculations need to be based on the limiting reactant.
• Example 2: What is the maximum mass of sulfur dioxide that can be produced by the reaction of 95.6 g carbon disulfide with 100. g oxygen?CS2 + 3O2 CO2 + 2SO2
Now solve the problem…
Calculations need to be based on the limiting reactant.• Example 2: What is the maximum mass of sulfur dioxide
that can be produced by the reaction of 95.6 g carbon disulfide with 100. g oxygen?CS2 + 3O2 CO2 + 2SO2
2
2
2
2
2
2
22 1611
1.64
1
2
2.76
16.95SOg
SOmol
SOg
CSmol
SOmol
CSg
CSmolCSg
22
2
2
2
2
22 1341
1.64
3
2
0.32
1.100SOg
SOmol
SOg
Omol
SOmol
Og
OmolOg
Which reactant is LIMITING?
Calculations need to be based on the limiting reactant.• Example 2: What is the mass of sulfur dioxide that can
be produced by the reaction of 95.6 g carbon disulfide with 100. g oxygen?CS2 + 3O2 CO2 + 2SO2
2
2
2
2
2
2
22 1611
1.64
1
2
2.76
16.95SOg
SOmol
SOg
CSmol
SOmol
CSg
CSmolCSg
22
2
2
2
2
22 1341
1.64
3
2
0.32
1.100SOg
SOmol
SOg
Omol
SOmol
Og
OmolOg
O2 limits the amount of SO2 that can be produced. CS2 is in excess.
Calculations need to be based on the limiting reactant.• Example 2: What is the mass of sulfur dioxide that can
be produced by the reaction of 95.6 g carbon disulfide with 100. g oxygen?CS2 + 3O2 CO2 + 2SO2
2
2
2
2
2
2
22 1611
1.64
1
2
2.76
16.95SOg
SOmol
SOg
CSmol
SOmol
CSg
CSmolCSg
22
2
2
2
2
22 1341
1.64
3
2
0.32
1.100SOg
SOmol
SOg
Omol
SOmol
Og
OmolOg
134 g of SO2 can be produced in this reaction.
Calculations need to be based on the limiting reactant.
• Example 3: What mass of CO2 could be formed by the reaction of 8.0 g CH4 with 48 g O2?
CH4 + O2 CO2 + H2O
Start by balancing the equation…
Calculations need to be based on the limiting reactant.
• Example 3: What mass of CO2 could be formed by the reaction of 8.0 g CH4 with 48 g O2?
CH4 + 2O2 CO2 + 2H2O
Now solve the problem…
Calculations need to be based on the limiting reactant.• Example 3: What mass of CO2 could be formed by the
reaction of 8.0 g CH4 with 48 g O2?
CH4 + 2O2 CO2 + 2H2O
22
2
4
2
4
44 221
0.44
1
1
0.16
10.8COg
COmol
COg
CHmol
COmol
CHg
CHmolCHg
22
2
2
2
2
22 331
0.44
2
1
0.32
148COg
COmol
COg
Omol
COmol
Og
OmolOg
Which reactant is LIMITING?
Calculations need to be based on the limiting reactant.• Example 3: What mass of CO2 could be formed by the
reaction of 8.0 g CH4 with 48 g O2?
CH4 + 2O2 CO2 + 2H2O
CH4 limits the amount of CO2 that can be produced. O2 is in excess.
22
2
4
2
4
44 221
0.44
1
1
0.16
10.8COg
COmol
COg
CHmol
COmol
CHg
CHmolCHg
22
2
2
2
2
22 331
0.44
2
1
0.32
148COg
COmol
COg
Omol
COmol
Og
OmolOg
Many chemical reactions do not go to completion (reactants are not completely converted to products).
Percent Yield: indicates what percentage of a desired product is obtained.
100yieldltheoretica
yieldalexperimentYield%
• So far, the masses we have calculated from chemical equations were based on the assumption that each reaction occurred 100%.
• The THEORETICAL YIELD is the yield calculated from the balance equation.
• The ACTUAL YIELD is the amount “actually” obtained in an experiment.
• Look back at Example 2. We found that 134 g of SO2 could be formed from the reactants.
• In an experiment, you formed 130 g of SO2. What is your percent yield?
%97100134
130%
g
gYield
Example: A 10.0 g sample of ethanol, C2H5OH, was boiled with excess acetic acid, CH3COOH, to produce 14.8 g of ethyl acetate, CH3COOC2H5. What percent yield of ethyl acetate is this?
CH3COOH + C2H5OH CH3COOC2H5 + H2O
5H
2COOC
3CH mol 1
5H
2COOC
3CH g 88
OH5
H2
C mol 1
5H
2COOC
3CH mol 1
OH5
H2
C 46g
OH5
H2
C mol 1OH5
H2
C 10.0g
5H
2COOC
3CH g1.19
Example: A 10.0 g sample of ethanol, C2H5OH, was boiled with excess acetic acid, CH3COOH, to produce 14.8 g of ethyl acetate, CH3COOC2H5. What percent yield of ethyl acetate is this?
100yieldltheoretica
yieldalexperimentYield%
100g 19.1g 14.8
Yield%
%5.77Yield%
