Download File - Mrs. Roy`s Science Class

Stoichiometry
Standard
 Students know how to determine the molar mass
of a molecule from its chemical formula and a
table of atomic masses and how to convert the
mass of a molecular substance to moles, number
of particles, or volume of gas at standard
temperature and pressure.
 Students know how to calculate the masses of
reactants and products in a chemical reaction
from the mass of one of the reactants or products
and the relevant atomic masses.
Turkey Sandwiches
2 Slices of Bread + 2 Slice of Cheese + 5 Slices Turkey  1 Turkey Sandwich
•If I have 6 slices of bread, how many sandwiches can I
make?
•How many slices of cheese and turkey will I need?
•If I want to make 38 turkey sandwiches (one for each person
in class), how many slices of bread, slices of cheese, and slices
of turkey will I need?
•How did you perform these calculations?
Chocolate Chip
Cookies
This recipe yields 4 dozen cookies
 1 cup butter, softened
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1 cup white sugar
1 cup packed brown sugar
2 eggs
2 teaspoons vanilla extract
3 cups all-purpose flour
1 teaspoon baking soda
2 teaspoons hot water
1/2 teaspoon salt
2 cups semisweet chocolate
chips
1 cup of chocolate chips = 60 g
1 cup flour= 125 g
1 cup butter= 227 g
1 cup sugar= 220 g
If you have 908 g of butter, how
many cookies can you make?
How many grams of chocolate
chips will you need?
Stoichiometry
 Greek for “measuring elements”
 Study of quantities of materials
consumed and produced in
chemical reactions.
 Qualitative
 Quantative
In terms of atoms and molecules:
 2H2 + O2 2H2O
Two molecules of hydrogen and one molecule
of oxygen form two molecules of water.
 2 Al2O3 Al + 3O2
2 molecules of aluminum oxide decompose to
form 4 atoms of aluminum and 3 molecules of
oxygen.
In terms of Moles
 2H2 + O2 2H2O
Two moles of hydrogen and one mole of
oxygen form two moles of water.
 2 Al2O3 Al + 3O2
2 moles of aluminum oxide decompose to form
4 moles of aluminum and 3 moles of oxygen.
In terms of Moles
2H2
2 moles
4 moles
10 moles
1 mole
?
?
+
O2
2H2O
1 mole
?
?
?
?
2.5 moles
2 moles
?
?
?
3.0 moles
?
In terms of Unit Analysis:
 2H2 + O2 2H2O
How many moles of water could be
produced by 2.00 mol of oxygen?
2.00 mol O2
2 mol H2O
1 mol O2
Ratio of coefficients
How many grams of water is that?
In terms of Unit Analysis:
 2H2 + O2 2H2O
How many moles of oxygen would be
needed to produce 5.00 mol of water?
5.00 mol H2 O
1 mol O2
2 mol H2 O
For every 2 moles
of water produced,
1 mole of oxygen
is needed
How many grams of oxygen is that?
Solving Stoichiometry Problems
Write these steps on the left side of your notebook
1. Your “recipe” (chemical rxn) calls for moles.
 If you are given the amount in grams or
molecules, convert to moles.
2. You are asked to determine how much
ingredients you need (reactants) or how
much of something you will end up with you
will make (products).
 Use ratio of coefficients to find how much is
needed.
3. If you are asked to find that amount in
grams/molecules, convert moles to the unit
you are asked to find.
 Mole to mass conversions (Molar mass)
and mole to molecules conversions
(Avogadro’s #) will always have the same
molecule/atom in the numerator and
denominator
Ex1 mol Al2O3
102 g Al2O3
NOT
1 mol O2
102 g Al2O3
This is like saying…
1 dozen donuts
102 g eggs
Practice Unit Analysis: Mole-Mass
 4Al + 3O2 2Al2O3
How many grams of aluminum oxide could
be produced by 4.00 mol of oxygen?
4.00 mol O2
2 mol Al2O3
3 mol O2
1 mol Al2O3
102 g Al2O3
Practice Unit Analysis: Mass-Mole
How many moles of chlorine are
required to react completely with 69.0
grams of sodium to produce sodium
chloride?
2 Na + Cl2  2 NaCl
69.0 g Na 1 mol Na
23 g Na
1 mol Cl2
2 mol Na
= 1.50 mol Cl2
Practice Unit Analysis: Mass-Mass
 Calculate how many grams of
ammonia are produced when you
react 28.0g of nitrogen with excess
hydrogen.
 N2 + 3 H2  2 NH3
Stoichiometry Organizer
MASS
MASS
MOLES
MOLES
VOLUME
VOLUME
Quiz 11-27
N2 + 3 H2  2 NH3
How many moles of H2
would be needed to
produce 1.8 mol of NH3?
Quiz 11-27a
N2 + 3 H2  2 NH3
How many moles of H2
would be needed to react
with 3.0 mol of N2?
Quiz 11-28 a
N2 + 3 H2  2 NH3
How many grams of NH3
could be produced by 1.0 mol
of N2?
Quiz 11-28 b
N2 + 3 H2  2 NH3
How many grams of NH3
could be produced by 3.0 mol
of H2?
Quiz 11-28 c
2 Na + Cl2  2 NaCl
How many moles of chlorine are
required to react completely with
69.0 grams of sodium to produce
sodium chloride?
Quiz 11-28 d
4 Al + 3O2  2 Al2O3
How many grams of aluminum
oxide could be produced by
27.0 g of aluminum?
Quiz 11-16
N2 + 3 H2  2 NH3
How many grams of NH3
could be produced by 15.0 g
of H2?
Quiz 11-17 a
N2 + 3 H2  2 NH3
How many grams of NH3
could be produced by 9.0 g of
H2?
Quiz 11-17 b
2 Na + Cl2  2 NaCl
How many grams of NaCl
could be produced by 140 g
of Cl2?
Quiz 11-17 c
CH4 + 2 O2  CO2 + 2 H2O
How many grams of H2O
could be produced by 64 g of
CH4?
Quiz 11-17 d
4 Fe + 3 O2  2 Fe2O3
How many grams of Fe2O3
could be produced by 112 g
of Fe?
Quiz 11-18 a
2 Mg + O2  2 MgO
How many grams of MgO
could be produced by 96 g of
O2?
Quiz 11-18 b
WO3 + 3 H2  W + 3 H2O
How many grams of W could
be produced by 6.0 g of H2?
Quiz 11-29
N2 + 3 H2  2 NH3
How many grams of NH3
could be produced by 89.6 L
of N2?
Quiz 12-17b
2 Na + Cl2  2 NaCl
How many grams of NaCl
could be produced by 89.6 L
of Cl2?
Quiz 11-28 a
4 Al + 3O2  2 Al2O3
How many grams of aluminum
oxide could be produced by
108 g of aluminum?
Quiz 11-28 b
4 Al + 3O2  2 Al2O3
How many liters of oxygen
would be needed to produce
34.0 g of aluminum oxide?