Chemical Quantities III
A.K.A. Stoichiometry
What is Stoichiometry?
 stoicheion (element; Greek) + metron
(measure; Greek)
 Quantitative relationship between
reactants and products
 Created by Jeremias Benjamin
Richter in 1792
How do we calculate the mass of a
product if we know the mass of a
reactant?
 How much water is produced when 1.5 g
of C6H12O6 is burned in oxygen?
C6H12O6 + O2  CO2 + H2O; Is it
balanced?
C6H12O6 + 6 O2  6 CO2 + 6 H2O
Create a Conversion Pathway
 We have 1.5 grams of C6H12O6; we need a mass-mass
conversion pathway
Step 1
Mass of
C6H12O6
Moles of
C6H12O6
Step 2
Step 3
Moles of
H2O
Mass of
H2O
C6H12O6 + 6 O2  6 CO2 + 6 H2O
Step 1
Mass of C6H12O6
Molar Mass
Moles of C6H12O6
1.5 g C6H12O6
1 mol C6H12O6
= 0.0083 mol
C6H12O6
180 g C6H12O6
Step 2
Moles of C6H12O6
Molar Ratio
Moles of H2O
0.0083 mol C6H12O6
6 mol H2O6
= 0.050 mol H2O
1 mol C6H12O6
Step 3
Moles of H2O
Molar Mass
Grams of H2O
0.050 mol H2O
18 g H2O
= 0.090 g H2O
1 mol H2O
Another Mass-Mass Conversion
 How much aluminum oxide is generated
with 2.3 g Al reacting with iron (III)
oxide
 Al + Fe2O3  Fe + Al2O3; is it balanced?
 2 Al + Fe2O3  2 Fe + Al2O3
2 Al + Fe2O3  2 Fe + Al2O3
Step 1
Mass of Al
Molar Mass
Moles of Al
2.3g Al
1 mol Al
= 0.085 mol Al
27 g Al
Step 2
Moles of Al
Molar Ratio
Moles of Al2O3
0.085 mol Al
1 mol Al2O3
= 0.043 mol Al2O3
2 mol Al
Step 3
Moles of Al2O3
Molar Mass
Mass of Al2O3
0.043 mol Al2O3
102 g Al2O3
= 4.3 g Al2O3
1 mol Al2O3
SmartBoard Exercise
Mass-Mass Conversions
It’s your turn to Team, Pair, Solo
 Chemical Quantities III Worksheet
 Complete the first problem as a team in
your row
 Complete the second problem as a pair
with the person on your right
 Complete the next few problems solo
Homework
 Read pp. 251-258
 Answer problems pg. 262: 31, 33, 35, 39,
40