Ch 9 stoichiometry Guided Reading Notes
9.1
Objectives
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Define Stoichiometry
Describe the importance of the mole ratio in stoichiometric calculations
Write a mole ratio relating two substances in a chemical reaction.
In stoichiometry problems you will be given the amount of at least one of the substances in a chemical equation and
asked to find the amount of one or more substances in the equation
The given amount may be expressed in ___________________ or ______________________________
The Unknown amount may be expressed in ____________________________ or ______________________What are the 4 types of stoichiometry problems?
What conversion factor do you use to change grams to moles?
All stoichiometry problems involve the use of the _____________________
Where do you get the mole ratio from?
What does the mole ratio enable you to do?
Can you perform a stoichiometry problem with an unbalanced chemical equation? Explain
9.1 assignment p 285 1 to 4
p 305 1 to 3
ws pages 1,2
9.2
Objectives
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Calculate the amount in moles of a reactant or product from the amount in moles of a different reactant or
product
Calculate the mass of a reactant or product from the amount in moles of a different reactant or product
Calculate the amount in moles of a reactant or product from the mass of a different reactant or product
Calculate the mass of a reactant or product from the mass of a different mass or product
Given moles, asked to find moles, use mole ratio
Do p 289, 1,2 Here are the balanced equations 3H2 + N2 2NH3,
2KClO3  2KCl + 3O2
Given mole, asked to find grams, Use molar mass to convert grams to moles, then use mole Ratio
Do p 291, 1 and 2
Given grams, asked to find moles, use molar mass to convert grams to moles, then mole ratio
Do p 293, 1,2 Here is the balanced equation
2HgO  2Hg + O2
Given grams, asked to find grams, use molar mass to convert grams to mole, use mole ratio to find unknown moles, use
molar mass to convert moles to grams
Do p 295, 1 to 3 here are the balanced equations for problems 2 and 3. Cu + 2AgNO3  2Ag + Cu(NO3)2,
2Al2O3 4Al + 3O2
9.2 assignment p 295 1 to 5
p 305 5 to 16
ws pages 3,4
9.3
Objectives
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Describe a method for determining which of 2 reactants is the limiting reactant
Calculate the amount in moles or mass in grams of a product, given the amount in moles or grams of 2 reactants,
one of which is in excess
Distinguish between theoretical yield, actual yield and percentage yield
Calculate percentage yield given the theoretical and actual yield of a product
What do you call the reactant that gets completely used up in a chemical reaction? What do you call the reactant that
does not get used up, that has some leftover?
The limiting reactant is not the reactant that is present in lesser amount (either in moles or grams). The mole ration
must be used to determine the liming reactant
To determine the limiting reacting when given the amount in moles of 2 reactants………….
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You need to choose one of the products, it doesn’t matter which. Use the same product for both
calculations below
For each reactant, use the amount of males of that reactant and the mole ratio to determine the
amount of product produced
Whichever reactant produces the least amount of product is the limiting reactant
P 297 problem 1
Most limiting reactant problems will give the amounts of two reactants in grams and ask you to find the amount in
grams of a specific product. It is important to recognize this as a limiting reactant problem. You will recognize a limiting
reactant problem because the amounts of TWO reactants will be given.
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Change grams to moles of both reactants
For each reactant, use the mole ratio to determine the amount in moles of unknown product produced.
Whichever reactant produces the least amount in moles of the product is the limiting reactant
Change the lesser amount of product in moles to grams to get the amount of product produced
To determine the amount of excess reactant leftover after the reaction is complete
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First determine the limiting reactant
Next use the limiting reactant and the mole ratio that exists between the limiting reactant and the
excess reactant to determine the amount of excess reactant that will be used.
Subtract the amount of excess reactant used from the given amount of excess reactant to get the
amount of excess reactant leftover.
P 299, problems 1,2
What is the theoretical yield? How is it different from the actual yield?
What are some reasons for the theoretical yield usually being greater than the actual yield?
The theoretical yield is the “right answer” when calculating a % error. It can also be called the “reference value or yield”
and it is the answer you get when solving a stoichiometry problem
The actual yield is the results you get when performing the experiment in the lab. It is also called the “experiment yield”
P 302 problems 1,2
Write the equations for percent yield and the equation for percent error. Notice the difference. Percent yield measures
the accuracy of your result (how close you are to the right answer) Percent error calculates the size of your error
compared to the magnitude of your answer.
Calculate the % yield and % error with this data: actual yield = 18 g, theoretical yield = 22g
Circle the right answers: You want your % error to be low/high and your % yield to be low/high
9.3 assignment
p 302, cp 1 to 3, adv 1 to 4 p 306 adv 17 to 30 cp 17 to 30
Ch 9 review assignment adv p 307 31 to 36, 39 p 309 1 to 13 ws 7,8
r96, 204 to 206 ws 7,8
ws 5,6
cp p 309 1 to 13, p r95 200 to 202, p