Chemistry 20
Quantitative Relationships in Chemical Changes
Your Assignment: pgs 1-2
Chapter 7: Stoichiometry
Stoichiometry and Quantitative Analysis
A. Using Mole Ratios
 ________________________________ is the study of the ______________
__________________________ of reactants and products in a ___________
________________________
 you can use the number of moles for a given reactant or product to find the
moles for any other reactant or product
Example
Consider the following chemical reaction:
2 C2H6(g) + 7 O2(g)  4 CO2(g) + 6 H2O(g)
1. Write the ratio for all components of the reaction.
2. What amount, in moles, of CO2(g) is formed if 2.50 mol of C2H6(g) reacts?
2 C2H6(g) + 7 O2(g)  4 CO2(g) + 6 H2O(g)
3. What amount, in moles, of O2(g) is required to react with 10.2 mol of
C2H6(g)?
2 C2H6(g)
+
7 O2(g)
 4 CO2(g) + 6 H2O(g)
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4. What amount, in moles, of H2O(g) is formed when 100 mmol of CO2(g) is
formed?
2 C2H6(g) + 7 O2(g)  4 CO2(g)
+ 6 H2O(g)
Your Assignment: pg 3
B. Gravimetric Stoichiometry
 gravimetric = _______________________________
Steps
1. Write a ________________________________ including the states.
Write the information ________________.
2. Find the __________ of the ______________ species using
3. Find the __________ of the ______________ species using
_____________________
4. Calculate ___________ of the wanted species using
Chemistry 20 Stoichiometry Notes
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Example 1
Iron is produced by the reaction of iron(III) oxide with carbon monoxide to
produce iron and carbon dioxide. What mass of iron(III) oxide is required to
produce 1000 g of iron?
Example 2
The decomposition of the mineral malachite, Cu2(CO3)(OH)2(s), yields
copper(II) oxide, carbon dioxide and water vapour. What mass of copper(II)
oxide is produced from 1.00 g of malachite?
Your Assignment: pgs 4-5
Chemistry 20 Stoichiometry Notes
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C. Solution Stoichiometry
 use _________________________ to perform calculations c = n/v
Example 1
What volume of 14.8 mol/L KOH is needed to react completely with 1.50 L of
12.9 mol/L sulphuric acid?
Your Assignment: pgs 6-7
D. Law of Combining Volumes
 you can use the Law of Combining Volumes when the pressure and
temperature conditions are constant for both the _______________________
__________________________________
Example
Consider the following reaction:
N2(g) + 2 O2(g)  N2O4(g)
a) What is the mole ratio for O2(g) and N2O4(g)?
b) What is the volume ratio for O2(g) and N2O4(g)?
Chemistry 20 Stoichiometry Notes
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c) If 1 mol of N2O4(g) is produced, how many moles of O2(g) must be
consumed?
d) If 1 L of N2O4(g) is produced, what volume of O2(g) must be
consumed?
e) If 2.5 L of N2(g) is consumed, what volume of O2(g) must be
consumed?
Your Assignment: pg 8
E. Gas Stoichiometry
 if the other information is given for the chemicals in the reaction (eg. mass),
use ________________________________ to perform calculations
Example 1
If 300 g of propane burns in a gas barbeque, what volume of oxygen at SATP is
required for the reaction?
Your Assignment: pgs 9-10
Chemistry 20 Stoichiometry Notes
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Chapter 8: Applications of Stoichiometry
8.1 Limiting and Excess Reagents
 let’s make double burgers…
1 bun + 2 meat patties  _______ double burger
2 buns + 4 meat patties  ________ double burgers
2 buns + 2 meat patties  _________ double burger
2 buns + one million meat patties  __________ double burgers
 limiting reagent = the _________________ that determines _____________
_____________________________________________ in a reaction
 excess reagent = the ____________________ that is present in ___________
_______________________ than necessary
Steps:
1. Write the _________________________________________________,
including states.
2. Calculate the __________________________________________ of
__________________________________ using
3. _____________________ the number of moles for ________________
by dividing by the _______________________ in the balanced
equation and compare…the one with the ________________ number of
moles is the _________________________________
4. Use ___________________________________________________ to
calculate the answer.
Chemistry 20 Stoichiometry Notes
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Example 1
When 80.0 g copper and 25.0 g of sulphur react, which reactant is limiting and
what is the maximum amount of copper(I) sulphide that can be produced?
Example 2
You are supplied with 9.00 g of KCl and 6.50 g of AgNO3. What is the mass of
the precipitate formed when these two chemicals react?
Chemistry 20 Stoichiometry Notes
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Example 3
A 200 mL sample of a 0.221 mol/L mercury (II) chloride solution reacts with
100.0 mL of a 0.500 mol/L solution of sodium sulfide. What is the mass of the
precipitate formed?
Your Assignment: pgs 11-12
8.2 Predicted and Experimental Yield
 the ________________________________________________ is called the
_____________________________________________________________
 the quantity of the product _____________________________ is called the
_____________________________________________________________
 it is _____________________________ for the predicted and experimental
yield to be ___________________
 factors affecting the experimental yield include:
Chemistry 20 Stoichiometry Notes
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1. two chemicals can react to give _______________________________
…called _______________________________________________
eg) _________________________________________________________
_________________________________________________________
2. reaction is very ___________________
3. ____________________________________________________ methods
4. reactant or product _______________________
5. reaction doesn’t go to _____________________________
 ideally, percent yield should be as close to _______________ as possible
 percent yield is calculated as follows:
 we can also calculate our ________________ for the experiment, which tells
us how far we are from the theoretical yield
 the closer to ____________ the percent error is, the _____________________
___________________________________________
Chemistry 20 Stoichiometry Notes
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Example 1
Calculate the % error and the % yield for the following:
predicted mass of ppt = 6.20 g
actual mass of ppt = 7.12 g
Example 2
Calculate the % error and the % yield for the following:
predicted mass of ppt = 100 g
actual mass of ppt = 93.5 g
Your Assignment: pg 13
Chemistry 20 Stoichiometry Notes
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8.3 Acid-Base Titration
A. Titration
 in solution stoichiometry, sometimes you don’t have enough information to
solve the problem on paper
eg) 10 mL of acetic acid reacts with a 0.202 mol/L NaOH solution. What is
the concentration of the acetic acid?

CH3COOH(aq)
+
NaOH(aq) 
H2O(l) +
NaCH3COO(aq)
x mol/L
c = 0.202 mol/L
v = 0.0100 L
v = ??? *****


 you need this volume in order to solve the problem
 a ___________________ is a _______________________ used to find the
_____________________ of substances so you can calculate
________________________________
 ______________________________________ is when a solution of
___________ concentration, a __________________________________, is
reacted with a solution of _________________ concentration
 both _____________________________________________need to be
_________________________________ since their concentrations will
____________________________________
 a solution called the __________________ is transferred from a precisely
marks tube called a ______________ to a ______________ containing the
______________ and an ______________________
 an indicator (eg. methyl orange, bromothymol blue) is used because a
_______________________________________________________
indicates the ___________________________________________________
 the endpoint is the point where the _________________________________
____________________________________________________
 equivalence point is the ______________________________________
_________________________________________________________
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 you need a minimum of 3 trials within ______________ of each other to
ensure results are accurate
Example
A 10.00 ml sample of HCl(aq) was titrated with a standardized solution of 0.685
mol/L NaOH(aq). Bromothymol blue indicator was used and it changes from
yellow to blue at the endpoint. What is the concentration of the HCl(aq)?
Note: HCl(aq) “is titrated with” NaOH
Titration Results: (sample data)
Trial
1
overshoot
2
Final Volume
(mL)
Initial Volume
(mL)
Volume
NaOH(aq) (mL)
Endpoint Colour
average volume =
Chemistry 20 Stoichiometry Notes
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3
4
Your Assignment: pg 14
B. Titration Curves
 a plot of the ____________________________________________________
is called a ______________________________________________
 titration curves are __________________________
 when a _______________________________________ is titrated with a
________________________________, the ___________________________
will always have a pH of ______ (at 25C)
 the ______________________ on the curve is always the ____________
______________________
 the pH changes ____________________________ at first…this is called the
_______________________________________
 as the endpoint is approached, the pH changes _____________________
 the __________________________ is _____________________ to the pH of
the __________________
Strong Acid Titrated with Strong Base
14
pH
7
0
volume of titrant added (mL)
Chemistry 20 Stoichiometry Notes
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Strong Base Titrated with Strong Acid
14
pH
7
0
volume of titrant added (mL)
C. Indicators for Titrations
 _________________ can be used to carry out a titration but it is much more
convenient to use an _________________
 the indicator should change colour ______________________________
________________________________________________________
 the pH of the endpoint should __________________________________
_______________________________________________________
Chemistry 20 Stoichiometry Notes
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