1. No category

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Chapter 9: Chemical Quantities or
Stoichiometry is
I. Information from Chemical Equations
II. Chemical Equations and Stoichiometry
A. Mole-Mole Relationships
B. Mass-Mole-Mole-Mass
Relationships
C. Limiting Reactants
D. Percent Yield
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I. Information from Chemical Equations
S(s) +
O2(g) +
H2O(g) 
H2SO4(l)
1. Equation must follow the law of conservation of mass.
2. Coefficients
- are called stoichiometric coefficients
- provide conversion factors
- refer to numbers of molecules, atoms,
formula units, or moles
Molecular Interpretation
Molar Interpretation
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II. Chemical Equations and Stoichiometry
A. Mole-Mole Relationships
If we combust 1.235 moles of butane (C4H10(g)) in
excess O2(g), how many moles of the following will
react or be produced?
C4H10(g) +
O2(g)  CO2(g) + H2O(g)
1. How many moles of O2 will react?
2. How many moles of CO2 will be produced?
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A. Mole-Mole Relationships Cont’d
If you produced 2.451 moles of CO2(g), how many
moles of O2(g) must have reacted?
2C4H10(g) + 13O2(g)  8CO2(g) + 10H2O(g)
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B. Mass-Mole-Mole-Mass Relationships
What mass of S8 is needed to react
with 2.45 g of H2?
8H2(g) + S8(s)  8H2S(g)
What mass of H2 is needed to produce 1.34x1023
molecules of H2S?
8H2(g) + S8(s)  8H2S(g)
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C. Limiting Reactants
Limiting ingredient (food) or reactant (chemistry)
ingredient or reactant that limits
the amount of food or chemical
product(s) that we can produce
Excess ingredients (food) or reactants (chemistry)
anything that doesn’t limit the
amount of product(s) we produce
How many sandwiches can we make if we have …..
2 pieces of bread –
4 pieces of tri-tip –
3 avocadoes –
4 tomatoes –
2 slices of lettuce –
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How many avocadoes will be left?
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Limiting Reactants and Chemistry
NO(g) + O2(g)  NO3(g)
1.
2.
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Calculations
If you react 5.00 grams of CaC2 with 5.00 grams
of H2O, how many grams of Ca(OH)2 can be
produced? How much of each reactant is left
after the reaction is complete?
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If you react 10.0 mg of Al with 10.0 mg of I2,
what is the mass of AlI3 that can be produced?
How much of each reactant is left after the
reaction is complete?
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D. Percent Yield
Urea (CN2H4O)
-
12th most synthesized chemical
Fertilizer (~46% N)
~150 million metric tons produced per year
$271 per metric ton ($325 last semester)
Chemical plant pictured produces ~1.2 million metric tons
per year
Boesch Moeller Process
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While in graduate school, you come up with a
new technique for combining NH3 and CO2 to
make urea. The first time you performed your
synthesis, you produced 3.00 g of urea when
2.00 g of NH3 reacted with excess CO2. What
was your percent yield? Should we talk to the
patent people?
2NH3(g) + CO2(g)  CN2H4O(s) + H2O(l)
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