Stoichiometry
Chapter 9
Do Now
Balance the equation
Al +
HCl →
H2 +
AlCl3
1. How many moles of HCl are required to produce 2 moles
of AlCl3 ?
2. How many moles of H2 can be produced from 2 moles of
Al?
3. List all other mole ratios that can be found from this
equation.
Vocabulary
Mole ratio- A conversion factor that relates the amount of moles
of any two substances involved in a chemical reaction
All reaction stoichiometry must start with a balanced chemical
equation.
Reaction Stoichiometry
Reaction stoichiometry problems can be classified
by the information given in the problem:
• The information that is given (known)
• The information that you are expected to find
(unknown)
• Three types of reactions are mole to mole, mole to
mass, and mass to mass.
Practice
How many moles of sodium will react with water to
produce 4.0 mol of hydrogen in the following
reaction?
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
Given:
4 mol hydrogen
Wanted: Moles of sodium
Mole to mole calculation /reaction
Practice
Phosphorus burns in air to produce a phosphorus
oxide in the following reaction:
4P(s) + 5O2(g) → P2O5(s)
What mass of phosphorus will be needed to
produce 3.25 mol of P2O5?
Given:
3.25 mol of P2O5?
Wanted: Mass of phosphorus
Mole to mass calculation /reaction
Practice
Calculate the mass of silver bromide produced
from 22.5 g of silver nitrate in the following
reaction.
2AgNO3(aq) + MgBr2 → 2AgBr(s) + Mg(NO3)2(aq)
Given:
22.5 g silver nitrate
Wanted: Mass of silver bromide
Mass to mass calculation /reaction
Mole to Mole Conversions
2Al+ 6 HCl → 3 H2 + 2 AlCl3
How many moles of H2 can be produced from 11.6 mol of
HCl?
Given:
11.6 mol HCl
Wanted: Moles of H2
Practice
How many moles of lithium chloride will be
formed by the reaction of chlorine with 0.046
mol of lithium bromide in the following reaction?
2LiBr(aq) + Cl2(g) → 2LiCl (aq) + Br2 (l)
Practice
Aluminum will react with sulfuric acid in the
following reaction.
2Al(s) + 3H2SO4(l) → Al2(SO4)3(aq) + 3H2(g)
How many moles of H2SO4 will react with 18 mol
Al?
Practice
Propane burns in excess oxygen according to
the following reaction.
C3H8 + 5O2 → 3CO2 + 4H2O
How many moles of CO2 are formed from 3.85
mol of propane?
Stop and Think
Why is the mole
ratio so important in
stoichiometrical
calculations?
Practice
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?
Practice
Ammonia, NH3, is widely used as a fertilizer and in many
household cleaners. How many moles of ammonia are
produced when 6 mol of hydrogen gas react with an
excess of nitrogen gas?
How many mol of nitrogen gas are required to produce
5 mol NH3 ?
Practice
The decomposition of potassium chlorate, KClO3,
into KCl and O2 is used as a source of oxygen in
the laboratory. How many moles of potassium
chlorate are needed to produce 15 mol of
oxygen gas?
Do Now
Given this equation: N2 + 3 H2 ---> 2 NH3, write
the following molar ratios:
a) N2 / H2
b) N2 / NH3
c) H2 / NH3
Practice
Answer the following questions for this equation: 2 H2 + O2 ---> 2 H2O
a) What is the H2 / H2O molar ratio?
b) Suppose you had 20 moles of H2 on hand and plenty of O2, how many
moles of H2O could you make?
c) What is the O2 / H2O molar ratio?
d) Suppose you had 20 moles of O2 and enough H2, how many moles of H2O
could you make?
Do Now
Use this equation: N2 + 3 H2 ---> 2 NH3, for the following problems
a) If you used 1 mole of N2, how many moles of NH3 could be produced?
b) If 10 moles of NH3 were produced, how many moles of N2 would be
required?
c) If 3.00 moles of H2 were used, how many moles of NH3 would be made?
d) If 0.600 moles of NH3 were produced, how many moles of H2 are
required?
Mole to Mass
1.Start with what you were given
2.Determine what is wanted
3.Determine your molar ratios
4.Use mole ratio to convert from one substance to
another
5.Convert from moles to mass
Practice
Phosphorus burns in air to produce phosphorus
oxide in the following reaction:
4P (s) + 5 O2(g) → P4O10 (s)
a.What mass of phosphorus will be needed to
produce 3.25 mol of P4O10 ?
b.If 0.489 mol of phosphorus burns, what mass of
oxygen is used?
c.What mass of P4O10 is produced?
Practice
Hydrogen peroxide breaks down, releasing
oxygen, in the following reaction.
2H2O2(aq) → 2H2O(l) + O2 (g)
a.What mass of oxygen is produced when 1.840
mol of H2O2 decompose?
b.What mass of water is produced when 5.0 mol
O2 is produced by this reaction?
Stoichiometry: Mole to Mass Homework
Page 890 in your textbook, # 171-172
Do Now
Mg(s) + 2HCl(aq)  MgCl2(aq) + H2(g)
a. How many grams of HCl are consumed by the
reaction of 2.50 moles of magnesium?
a. What is the mass in grams of H2 gas when 4.0
moles of HCl is added to the reaction?
Mass to Mass
1. Start with what you were given
1. Determine what is wanted
2. Determine your molar ratios
3. Convert from mass to mole
4. Use mole ratio to convert from one substance to another
5. Convert from moles to mass
Practice
Calculate the mass of silver bromide produced from 22.5 g
of silver nitrate in the following reaction.
2AgNO3 (aq) + MgBr2(aq) → 2AgBr(s) + Mg(NO3)2 (aq)
Practice
What mass of acetylene, C2H2, will be produced
from the reaction of 90g of calcium carbide,
CaC2, with water in the following reaction?
CaC2(s) + 2 H20(l) → C2H2(g) + Ca(OH)2(s)
Stoichiometry: Mass to Mass homework
Page 890 in your textbook, # 175