Mass Relationships
and Stoichiometry
Mole Ratio
• Recall: The coefficients of a balanced chemical
equation give the mole ratio of one chemical
to another
• We can use these numbers to predict the
number of moles of product produced
• We calculate moles using the mass and molar
mass of a compound:
n=
m
M
We Can Use Stoichiometry
to Find Mass!
A typical astronaut exhales 8.83 x 102 g of carbon dioxide
daily. Determine the mass of lithium hydroxide required to
react with this mass of CO2.
CO2(g) + 2LiOH(aq)  Li2CO3(aq) + H2O(l)
1.
2.
3.
4.
Write the balanced chemical equation
Convert mass to moles using mole equation
Use the mole ratio to predict moles of other substance
Convert moles to mass using mole equation
We Can Use Stoichiometry
to Find Mass!
A typical astronaut exhales 8.83 x 102 g of carbon dioxide
daily. Determine the mass of lithium hydroxide required to
react with this mass of CO2.
CO2(g) + 2LiOH(aq)  Li2CO3(aq) + H2O(l)
1.
2.
3.
4.
Write the balanced chemical equation
Convert mass to moles using mole equation
Use the mole ratio to predict moles of other substance
Convert moles to mass using mole equation
We Can Use Stoichiometry
to Find Mass!
A typical astronaut exhales 8.83 x 102 g of carbon dioxide
daily. Determine the mass of lithium hydroxide required to
react with this mass of CO2.
CO2(g) + 2LiOH(aq)  Li2CO3(aq) + H2O(l)
1.
2.
3.
4.
Write the balanced chemical equation
Convert mass to moles using mole equation
Use the mole ratio to predict moles of other substance
Convert moles to mass using mole equation
Examples
An automobile airbag is inflated with nitrogen
produced from the decomposition of sodium azide,
NaN3. The mass of nitrogen in a fully inflated airbag
is 87.5 g. What mass of sodium azide is required to
produce this mass of nitrogen?
A typical antacid tablet contains 0.50 g of calcium
carbonate. What mass of hydrochloric acid will this
mass of calcium carbonate neutralize?
Homework
Read
Section 7.2
Questions
Worksheet
p. 324 #2-3
p. 325 # 3, 6, 7, 9
https://www.youtube.com/watch?v=7UkmX9Ps
VDE