Chapter 5
Chemical Reactions and
Quantities
Mole Relationships in
Chemical Equations
LecturePLUS Timberlake 99
1
Mole-Mole Factors
 Show the mole-to-mole ratio between two
of the substances in a balanced equation
 Use the coefficients of two substances in
the equation
LecturePLUS Timberlake 99
2
Writing Mole Factors
4 Fe + 3 O2
2 Fe2O3
Fe and O2 4 mole Fe and 3 mole O2
3 mole O2
4 mole Fe
Fe and Fe2O3 4 mole Fe and 2 mole Fe2O3
2 mole Fe2O3
4 mole Fe
O2 and Fe2O3 3 mole O2 and 2 mole Fe2O3
2 mole Fe2O3
3 mole O2
LecturePLUS Timberlake 99
3
Learning Check S1
3 H2(g) + N2(g)
2 NH3(g)
A. A mole factor for H2 and N2 is
1) 3 mole N2
2) 1 mole N2
3) 1 mole N2
1 mole H2
3 mole H2
2 mole H2
B. A mole factor for NH3 and H2 is
1) 1 mole H2
2 mole NH3
2) 2 mole NH3
3 mole H2
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3) 3 mole N2
2 mole NH3
4
Solution S1
3 H2(g) + N2(g)
2 NH3(g)
A. A mole factor for H2 and N2 is
2) 1 mole N2
3 mole H2
B. A mole factor for NH3 and H2 is
2) 2 mole NH3
3 mole H2
LecturePLUS Timberlake 99
5
Chemical Calculations
4 Fe
+
3 O2
2 Fe2O3
How many moles of Fe2O3 are produced when
6.0 moles O2 react?
6.0 mole O2 x 2 mole Fe2O3 = 4.0 mole Fe2O3
3 mole O2
LecturePLUS Timberlake 99
6
Learning Check S2
4 Fe
+
3 O2
2 Fe2O3
How many moles of Fe are needed to react
with 12.0 mole of O2?
1) 3.00 mole Fe
2) 9.00 mole Fe
3) 16.0 mole Fe
LecturePLUS Timberlake 99
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Solution S2
4 Fe
+
3 O2
12.0 mole O2 x
2 Fe2O3
4 mole Fe = 16.0 mole Fe
3 mole O2
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Learning Check S 3
4 Fe
+
3 O2
2 Fe2O3
How many grams of O2 are needed to produce
0.400 mole of Fe2O3?
1) 38.4 g O2
2) 19.2 g O2
3) 1.90 g O2
LecturePLUS Timberlake 99
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Solution S 3
2) 19.2 g O2
0.400 mole Fe2O3 x 3 mole O2 x 32.0 g O2
2 mole Fe2O3 1 mole O2
= 19.2 g O2
LecturePLUS Timberlake 99
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Mass of A Reaction
The reaction between H2 and O2 produces
13.1 g of water. How many grams of O2
reacted?
Write the equation
H2 (g)
+ O2 (g)
H2O (g)
Balance the equation
2 H2 (g)
+ O2 (g)
LecturePLUS Timberlake 99
2 H2O (g)
11
Organize data
mole bridge
2 H2 (g)
Plan
+ O2 (g)
?g
g H 2O
mole H2O
2 H2O (g)
13.1 g
mole O2
O2
Setup
13.1 g H2O x 1 mole H2O x 1 mole O2 x 32.0 g O2
18.0 g H2O 2 mole H2O 1 mole O2
= 11.6 g O2
LecturePLUS Timberlake 99
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Points to Remember
1. Read an equation in moles
2. Convert given amount to moles
3. Use mole factor to give desired
moles
4. Convert moles to grams
grams (given)
grams (desired)
moles (given)
moles
(desired)13
LecturePLUS Timberlake
99
Learning Check S 4
How many grams of O2 are need to react
50.0 grams of Na in the reaction
4 Na +
O2
2 Na2O
Complete the set up:
50.0 g Na x 1 mole Na x ________ x _______
23.0 g Na
LecturePLUS Timberlake 99
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Solution S 4
4 Na +
O2
2 Na2O
50.0 g Na x 1 mole Na x 1 mole O2 x 32.0 g
23.0 g Na
=
4 mole Na
1 mole O2
g O2
LecturePLUS Timberlake 99
15
Learning Check S5
Acetylene gas C2H2 burns in the oxyactylene
torch for welding. How many grams of C2H2
are burned if the reaction produces 75.0 g of
CO2?
2 C2H2 + 5 O2
4 CO2 + 2 H2O
LecturePLUS Timberlake 99
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Solution S5
2 C2H2 + 5 O2
4 CO2 + 2 H2O
75.0 g CO2 x 1 mole CO2 x 2 mole C2H2 x 26.0 g C2H2
44.0 g CO2
4 mole CO2
1 mole C2H2
= 22.2 g C2H2
LecturePLUS Timberlake 99
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Pathways for Problems Using
Equations
Given (A)
grams (A)
Find (B)
grams (B)
moles (A)
moles (B)
particles (A)
LecturePLUS Timberlake 99
particles (B)
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Pathways for Problems Using
Equations
Given (A)
grams (A)
molar
mass (A)
Find (B)
grams (B)
molar
mass (B)
coefficients
moles (A)
Avogadro's
number
particles (A)
moles (B)
Avogradro’s
number
LecturePLUS Timberlake 99
particles (B)
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