Stoichiometry Notesheets
Name________________________________
The Mathematics of Chemical Equations
Period______Date______________________
9.1: Balanced Chemical Equations
1. Provides qualitative and quantitative information.
2. Supports the Law of ____________________________________________________
3.
2H2
+
O2
→
2H2O
The above equation is interpreted in terms of particles as follows:
A. _____________________ of H2 react with _________________ of O2 to produce
_______________________ of water. The ratio of H2 to O2 to water is ___________.
Or
B. 20 molecules of H2 react with _______ molecules of O2 to produce _______ molecules of
water. The ratio of H2 to O2 to water is ________________.
C. The original equation can then be interpreted as follows:
2 moles of H2 react with _______ mole of O2 to produce ______ moles of water.
The ratio of H2 to O2 to water is ________________.
D. It is more convenient to interpret the coefficients as the number of moles, because we
measure amounts of substances by _______________ in the laboratory. We can convert
between grams and moles in solving problems involving chemical reactions.
4. Stoichiometry: The study of the ________________________________________________________
that exist in a formula and in a chemical reaction.
5. The word Stoichiometry comes from the Greek word “stoicheion” meaning ______________________,
and “metron”, meaning __________________________.
6. Importance: The safe, economical and ____________________________ manufacture of chemicals
(or food) and the safe administration of pharmaceuticals.
7. Proof: The Law of Conservation of Mass is shown by the ______________________ equation, or by
adding up all the masses of reactants and products to determine if they are equal.
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8. Mole-Mole Problems require 3 steps to determine the molar ratio: Stoichiometryville Map
A. _______________________________
B. _________________________________________________________________________
C. _________________________________________________________________________
Ex #1) Ammonium nitrate decomposes into dinitrogen monoxide and water. How many moles of
dinitrogen monoxide and water are produced from 2.25 moles of reactants?
Equation:
Ratio:
2.25 mol NH4NO3
2.25 mol NH4NO3
Ex #2) Hydrochloric acid reacts with zinc in a single replacement reaction. How many moles of
hydrochloric acid are needed to react with 2.3 moles of Zn?
Equation:
Ratio:
Stoichiometry Problems:
1. A balanced equation represents a chemical reaction that conforms to the
______________________________________________________________________
2. _________________________ can NEVER be changed to balance a chemical equation.
3. The total ____________ of the reactants is the same as the total ____________ of the products.
4. Coefficients in a balanced equation relate _______________ of substances in the reaction.
5. Coefficients are used in constructing the _____________ ____________ for a stoichiometric problem.
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6. Grams of the known must first be converted to ______________, then use the ________________
_____________ to relate the 2 substances, finally convert the moles of the unknown to ____________.
7. Mass-Mass Problems:
Ex #1) What mass of aluminum oxide can be prepared by the reaction of 67.5 g of Al and oxygen?
Ex #2) Glucose is used as an energy source by the human body. Calculate the number of grams of
oxygen needed to oxidize (burn) 12.5 g of glucose. Write the balanced combustion reaction:
C6H12O6
+
O2
→
Ex #3) During WWII Germany used a method called the Haber Process to produce ammonia for
explosives. Today a similar process is used to make fertilizers. If an excess of nitrogen is reacted
with 1.71 mol of hydrogen, how many grams of ammonia, NH3, is produced?
Ex #4) Iron will react with oxygen gas to produce iron (III) oxide. How many grams of iron (III) oxide
will be produced if 0.18 mol of iron reacts?
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8. Mass-Volume Problems:
Ex) Airbags contain a powder called sodium azide (NaN3). When exposed to a spark the sodium azide
quickly decomposes into sodium and nitrogen gas. If an uninflated airbag contains 125 g of NaN3,
what volume in liters of nitrogen gas will be produced at STP?
NaN3 →
9. Volume –Volume Problems:
Ex) What volume in liters of hydrogen gas is needed to react completely with 15.5 L of nitrogen gas to
produce ammonia gas (NH3) at STP?
10. Mass-Particles Problems:
Ex) How many particles of barium hydroxide are produced from the single replacement reaction of
barium and 9.54 g of water?
11. Volume-Particles Problems:
Ex) How many liters of hydrogen gas are produced from the single replacement reaction of calcium with
6.09 x1023 molecules of hydrochloric acid?
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9.2: % Yield
1. Expected Yield: (Theoretical Yield) Amount of _______________ that should be produced based on
_____________________________________.
2. Actual Yield: Amount of _________________ actually obtained in the _________________________.
3. % Yield: .
% Yield =
4. % Error:
% error =
expected - actual
x 100% =
expected
Ex) Lauren burned 4.789 g of magnesium . At the end of the experiment she weighed 7.250 g of product.
What is the % yield and the % error for these results?
• 1st write and balance the equation.
• 2nd calculate the expected yield from the equation.
• 3rd calculate the % yield and % error from the above data.
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5. Limiting Reactant The limiting reactant is the _____________________ substance that becomes used
up ____________ when a chemical reaction occurs. It controls how ___________________ or
how _________________ product can be formed.
Ex) If a recipe for 1 cake is:
2 cups flour and your kitchen contains
2 eggs
1 cup sugar
1½Tbls. baking powder
1 cup water
⅓ cup oil
7 cups flour
2 dozen eggs
9 cups sugar
10 Tbls. baking pwdr
unlimited water
3⅓ cups oil
How many cakes can you make given the ingredients present in your kitchen? _______
What ingredient is the limiting reactant? __________________ How many eggs are left over
after making the cakes? ___________
6. Look at the following reaction:
NH3
+
O2 → NO +
H2O.
In an experiment, 3.25 g of NH3 are reacted with 3.50 g of O2. How many grams of NO are formed?
What is the most NO that can be produced? ___________________
Which reactant is the limiting reagent? ____________________
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