Modern Chemistry
Chapter 9
Stoichiometry
Sections 1-3
Introduction to Stoichiometry
Ideal Stoichiometric Calculations
Limiting Reactant and Percent Yield
Chapter 9 Vocabulary
•
•
•
•
•
•
•
•
Composition Stoichiometry
Reaction Stoichiometry
Mole Ratio
Limiting Reactant
Excess Reactant
Actual Yield
Theoretical Yield
Percent Yield
Chapter 9 Section 1
Introduction to Stoichiometry
Chapter 9 Section 1 Intro.
Stoichiometry pages 299-303
Definitions
• Composition stoichiometry deals with the
mass relationships of elements in compounds.
• Reaction stoichiometry involves the mass
relationships between reactants and products in
a chemical reaction.
Chapter 9 Section 1 Intro.
Stoichiometry pages 299-303
Stoichiometry Animation
p. xx
Chapter 9 Section 1 Intro.
Stoichiometry pages 299-303
Definitions
• A mole ratio is a conversion factor that relates
the amounts in moles of any two substances
involved in a chemical reaction
Example:
2Al2O3(l)  4Al(s) + 3O2(g)
Mole Ratios:
2 mol Al2O3 2 mol Al2O3
4 mol Al
3 mol O2
Chapter 9 Section 1 Intro.
Stoichiometry pages 299-303
4 mol Al
3 mol O2
Using the Mole Ratio
p. xx
Chapter 9 Section 1 Intro.
Stoichiometry pages 299-303
Mole – Mole Examples
Mg(s) + 2HCl(aq)  MgCl2(aq) + H2(g)
• If 2 mol of HCl react, how many moles of H2 are
obtained?
• How many moles of Mg will react with 2 mol of
HCl?
• If 4 mol of HCl react, how many mol of each
product are produced?
• How would you convert from moles of
substances to masses?
Chapter 9 Section 1 Intro.
Stoichiometry pages 299-303
Converting from gmol
p. xx
Chapter 9 Section 1 Intro.
Stoichiometry pages 299-303
Section 1 Homework
Page 301 #1-4
Chapter 9 Section 1 Intro.
Stoichiometry pages 299-303
Chapter 9 Section 2
Ideal Stoichiometric Calculations
Chapter 9 Section 2 Ideal
Stoichiometry pages 304-311
Reactants

MASS OF
SUBSTANCE
GIVEN
Products
MASS OF
SUBSTANCE
WANTED
MOLAR
MASS
MOLAR
MASS
MOLES OF
SUBSTANCE
GIVEN
MOLES OF
SUBSTANCE
WANTED
MOLE RATIO
Chapter 9 Section 2 Ideal
Stoichiometry pages 304-311
Tool Box
Chapter 9 Section 2 Ideal
Stoichiometry pages 304-311
mg
Kg
L
g
mL
MOLES
MOLES
mL
g
L
mg
Kg
Chapter 9 Section 2 Ideal
Stoichiometry pages 304-311
Sample Problem
How many kilograms of ethane are required to
react with excess oxygen to produce 8.70 L of
carbon dioxide? The density of carbon dioxide
gas at standard temperature is 1.799 g/L.
0.00535 kg
Chapter 9 Section 2 Ideal
Stoichiometry pages 304-311
mg
Kg
L
g
mL
MOLES
MOLES
mL
g
L
mg
Kg
Chapter 9 Section 2 Ideal
Stoichiometry pages 304-311
C2H6 (g) + O2 (g)  CO2 (g) + H2O
? Kg
g
MOLES
MOLES
x
+E
8.70L
g
L CO2
(g)
g CO2 mol CO2 mol C2H6
g C2H6 kg C2H6
x
x
x
x
L CO2
g CO2 mol CO2 mol C2H6 g C2H6
Chapter 9 Section 2 Ideal
Stoichiometry pages 304-311
C2H6 (g) + O2 (g)  CO2 (g) + H2O
8.70L
g
g
MOLES
MOLES
L CO2
x
+E
1000g=1Kg
? Kg
(g)
g CO2 mol CO2 mol C2H6 g C2H6 kg C2H6
x
x
x
x
L CO2
g CO2 mol CO2 mol C2H6 g C2H6
Chapter 9 Section 2 Ideal
Stoichiometry pages 304-311
Sample Problem p. 306
In photosynthesis, plants use energy from the sun
to produce glucose, C6H12O6, and oxygen from
the reaction of carbon dioxide and water.
What mass, in grams, of glucose is produced
when 3.00 mol of water react with carbon
dioxide?
90.1 g C6H12O6
mol-mass
Chapter 9 Section 2 Ideal
Stoichiometry pages 304-311
Sample Problem p. 310
Tin (II) fluoride, SnF2, is used in some
toothpastes. It is made by the reaction of tin
with hydrogen fluoride according to the
following equation.
Sn(s) + 2HF(g)  SnF2(s) + H2(g)
How many grams of SnF2 are produced from
the reaction of 30.00 g HF with Sn?
117.5 g SnF2
mass-mass.
Chapter 9 Section 2 Ideal
Stoichiometry pages 304-311
Sample Problem p. 305
In a spacecraft, the carbon dioxide exhaled by
astronauts can be removed by its reaction with
lithium hydroxide, LiOH, according to the
following chemical equation.
CO2(g) + 2LiOH(s)  Li2CO3(s) + H2O(l)
How many moles of lithium hydroxide are
required to react with 20 mol CO2, the average
amount exhaled by a person each day?
mol-mol
Chapter 9 Section 2 Ideal
Stoichiometry pages 304-311
40 mol LiOH
Sample Problem p. 309
The first step in the industrial manufacture of
nitric acid is the catalytic oxidation of ammonia.
NH3(g) + O2(g)  NO(g) + H2O(g) (unbalanced)
The reaction is run using 824 g NH3 and excess
oxygen.
a. How many moles of NO are formed?
b. How many moles of H2O are formed?
48.4mol NO; 72.5 mol H2O
mass-mol
Chapter 9 Section 2 Ideal
Stoichiometry pages 304-311
Problem
Magnesium burns in oxygen to produce
magnesium oxide. How many grams
magnesium will burn in the presence of 189 mL
of oxygen? The density of oxygen is 1.429g/L.
0.410 g Mg
mL-g
Chapter 9 Section 2 Ideal
Stoichiometry pages 304-311
Problem
Limestone, CaCO3, can be decomposed with
heat to form lime, CaO, and carbon dioxide.
How many moles of lime would be formed from
the decomposition of 20.1 kilograms of
limestone?
201 moles CaO
Kg-mol.
Chapter 9 Section 2 Ideal
Stoichiometry pages 304-311
Section 2 Homework
Page 311 #1-5
Chapter 9 Section 2 Ideal
Stoichiometry pages 304-311
Section 2 Homework
Problem Bank
Page 890-892 #176, 177, 179,
180, 184, 187, 190, 191, 192,
194, 196
Chapter 9 Section 2 Ideal
Stoichiometry pages 304-311
Chapter 9 Section 3
Limiting Reactant and Percent Yield
Chapter 9 Section 3 Limiting
Reactant pages 312-318
Definitions
• The limiting reactant is the reactant that
limits the amount of the other reactant that can
combine and the amount of product that can
form in a chemical reaction.
• The excess reactant is the substance that is
not used up completely in a reaction.
Chapter 9 Section 3 Limiting
Reactant pages 312-318
S’mores
• Given the bag o’ reactants find the number of
s’mores you could produce if the balanced
equation is
• 2 Tg + 1 Mm  1 Sm
• Tg = Teddy Graham
• Mm = Minimarshmallow
• Sm = S’more
Chapter 9 Section 3 Limiting
Reactant pages 312-318
S’mores
•
•
•
•
•
•
What is the limiting reactant?
What is the reactant in excess?
What is the amount in excess ?
What is the theoretical yield?
What is the actual yield?
What is the percent yield?
Chapter 9 Section 3 Limiting
Reactant pages 312-318
Sample Problem p. 313
Silicon dioxide (quartz) is usually quite unreactive
but reacts readily with hydrogen fluoride
according to the following equation.
SiO2(s) + 4HF(g)  SiF4(g) + 2H2O(l)
If 6.0 mol HF is added to 4.5 mol SiO2, which is
the limiting reactant?
HF
mol & mol limiting
Chapter 9 Section 2 Ideal
Stoichiometry pages 304-311
Problem
I need a problem that requires them to answer
these questions
a.Which compound is the limiting reactant?
b.What is the theoretical yield of product?
c.What is the reactant in excess, and how much
remains after the reaction is completed?
8.940 x 1023 molecules
mass & mass, limiting, actual
Chapter 9 Section 3 Limiting
Reactant pages 312-318
Problem
I need another problem that requires them to
answer these questions
a.Which compound is the limiting reactant?
b.What is the theoretical yield of product?
c.What is the reactant in excess, and how much
remains after the reaction is completed?
8.940 x 1023 molecules
mass & mass, limiting, actual
Chapter 9 Section 3 Limiting
Reactant pages 312-318
Limiting Reactant
p. xx
Chapter 9 Section 3 Limiting
Reactant pages 312-318
Section 3 Homework
Page 318 #1 & 2
Chapter 9 Section 3 Limiting
Reactant pages 312-318
Definitions
• The theoretical yield is the maximum amount
of product that can be produced from a give
amount of reactant.
• The actual yield is the measured amount of
product obtained from a reaction.
• The percentage yield is the ratio of the actual
yield to the theoretical yield, multiplied by 100.
Chapter 9 Section 3 Limiting
Reactant pages 312-318
Percent Yield
p. xx
Chapter 9 Section 3 Limiting
Reactant pages 312-318
Sample Problem p. 317
Chlorobenzene, C6H5Cl, is used in the production
of many important chemicals, such as aspirin,
dyes, and disinfectants. One industrial method
of preparing chlorobenzene is to react benzene,
C6H6, with chlorine, as represented by the
following equation.
C6H6 (l) + Cl2 (g)  C6H5Cl (l) + HCl (g)
When 36.8 g C6H6 react with an excess of Cl2,
the actual yield of C6H5Cl is 38.8 g.
What is the percentage yield of C6H5Cl?
mass-mass percent
Chapter 9 Section 2 Ideal
Stoichiometry pages 304-311
73.2%
Problem
Hydrogen sulfide gas can be formed by the action
of HCl and FeS, forming FeCl2 as product.
What is the theoretical yield in molecules of
hydrogen sulfide if 130.5 g of FeS are mixed
with 150.0 g of HCl? If the percent yield in the
lab is 93.6% what is the actual yield?
8.940 x 1023 molecules
mass & mass, limiting, actual
Chapter 9 Section 3 Limiting
Reactant pages 312-318
Benzene, C6H6, is reacted
with bromine, Br2, to
Problem
produce bromobenzene, C6H5Br, and hydrogen
bromide, HBr, as shown below. When 40.0 g of
benzene are reacted with 95.0 g of bromine,
65.0 g of bromobenzene is produced.
C6H6 + Br2  C6H5Br + HBr
a.Which compound is the limiting reactant?
b.What is the theoretical yield of bromobenzene?
c.What is the reactant in excess, and how much
remains after the reaction is completed?
d.What is the percentage yield?
Benzene,
80.4g,
Br2 13.2g, 80.8%
Chapter
9 Section 2 Ideal
Stoichiometry pages 304-311
Molarity
• Molarity measures the concentration of
solutions. (aq)
• Molarity = moles / liter
3 mol
3M =
1 L
Chapter 9 Section 3 Limiting
Reactant pages 312-318
Problem
When 20.0 mL of 0.90M solution of lithium nitrate
and 15.0 mL of 0.40M solution of calcium
phosphate react, a precipitate is formed. The
mass of the precipitate produced in the lab is
0.66 grams. What is the reactant in excess, the
limiting reactant, the amount in excess, the
theoretical yield and the percent yield.
0.69 grams theo.
Chapter 9 Section 3 Limiting
Reactant pages 312-318
Section 3 Homework
Problem Bank
Page 892-894 #201, 208, 214,
217, 219, 223, 226, 229, 232
Chapter 9 Section 3 Limiting
Reactant pages 312-318