What is stoichiometry?
A problem solving method used to calculate the amount of
product made or amount of reactant needed in a chemical
reaction
What is a mole?
A mole is the measurement for the amount of a substance.
1 mole = molar mass (g) of substance
What is the mole ratio?
Ratio of moles of one substance to moles of another
substance. Use the coefficients from balanced equation.
2H2 + O2  2H2O
Ratio of H2 to O2 ?
Ratio of H2 to H2O?
Ratio of O2 to H2O?
2:1
2:2
1:2
Review: Calculate molar mass of Cu(NO3)2
Cu = 1 x 63.55 = 63.55
N = 2 x 14.01 = 28.02
O = 6 x 16.00 = 96.00
187.57 g/mol
Remember: round all masses to 2 places past decimal
Conservation of Mass
- What is conserved in a chemical reaction?
- total mass
- # of atoms of each element
- What is NOT conserved in a chemical reaction?
- # of moles - # of molecules
One disadvantage of burning propane (C3H8) is that carbon dioxide is one
of the products. The released carbon dioxide increases the growing
amount in the atmosphere. How many moles of carbon dioxide are
produced when 10.0 moles of propane are burned in excess oxygen in a
gas grill?
C3H8 + 5O2
10 mol
10 mol C3H8

3CO2
? mol
+
4H2O
3 mol CO2 = 30 mol CO2
1 mol C3H8
How many moles of ammonia (NH3) are produced when 0.60 moles of
nitrogen react with hydrogen?
N2
+
3H2
0.60 mol
0.60 mol N2
2 mol NH3 =
1 mol N2

2NH3
Zinc reacts with iodine in a synthesis reaction. Determine the theoretical
yield if a 125.0 g sample of zinc was used. Determine the percent yield if
515.6 g product is recovered.
Zn +
125.0 g
125.0 g Zn 1 mol Zn
I2

ZnI2
?g
1 mol ZnI2 319.19 g ZnI2 = 610.2 g ZnI2
65.39 g Zn 1 mol Zn
1 mol ZnI2
? mol
1.2 mol NH3
Actual_____ x 100
Theoretical
515.6 g ZnI2 x 100 = 84.50 %
610.2 g ZnI2
A solution of potassium chromate reacts with a solution of lead (II)
nitrate. Starting with 0.250 moles of potassium chromate, determine the
mass of the lead (II) chromate produced.
Aluminum chloride is an inexpensive reagent used in many industrial
processes. It is made by treating scrap aluminum with chlorine. If you
start with 2.70 g of aluminum and 4.05 g of chlorine, which reactant is
limiting? How many grams of aluminum chloride are produced?
2Al +
2.70 g
2.70 g Al 1 mol Al
Pb(NO3)2

PbCrO4
?g
+
2KNO3
0.250 mol K2CrO4 1 mol PbCrO4 323.19 g PbCrO4 = 80.8 g PbCrO4
1 mol K2CrO4
3Cl2  2AlCl3
4.05 g
?g
1 mol PbCrO4
What is the theoretical yield of sodium chloride (i.e. calculate the grams)
produced when 1.25 moles of chlorine gas reacts vigorously with sodium.
2 mol AlCl3 133.34 g AlCl3 =
26.98 g Al 2 mol Al
K2CrO4 +
0.250 mol
13.3 g AlCl3
2Na
1 mol AlCl3
+
LR = Cl2
Cl2 
1.25 mol
2NaCl
?g
because it makes less AlCl3
4.05 g Cl2 1 mol Cl2 2 mol AlCl3 133.34 g AlCl3
70.9 g Cl2 3 mol Cl2
1 mol AlCl3
=
5.08 g AlCl3
1.25 mol Cl2
2 mol NaCl 58.44 g NaCl
1 mol Cl2
1 mol NaCl
= 146 g NaCl
One in a series of reactions that inflate air bags in automobiles is the
decomposition of sodium azide (NaN3). Determine the number of moles
of N2 produced if 100.0 g of NaN3 is decomposed.
2NaN3  3N2
100.0 g
? mol
100.0 g NaN3
+
Ammonium nitrate, an important fertilizer, produces dinitrogen monoxide
gas and water when it decomposes. Calculate the grams of water produced
from the decomposition of 25.0 g of solid ammonium nitrate.
2Na
NH4NO3
25.0 g
1 mol NaN3
3 mol N2
= 2.307 mol N2
65.01 g NaN3 2 mol NaN3

25.0 g NH4NO3 1 mol NH4NO3
N2O
+
2 mol H2O
80.04 g NH4NO3 1 mol NH4NO3
Solid silicon dioxide, often called silica, reacts with hydrofluoric acid
solution to produce the gas silicon tetrafluoride and water. How many
moles of acid are needed to produce 60.0 grams of silicon tetrafluoride?
SiO2
60.0 g SiF4
+
4HF  SiF4 +
? mol
60.0 g
18.02 g H2O = 11.3 g H2O
1 mol H2O
Determine the mass of CO2 produced from the combustion of 100.0 g
ethanol (C2H5OH).
C2H5OH
2H2O
1 mol SiF4
4 mol HF = 2.31 mol HF
104.08 g SiF4 1 mol SiF4
2H2O
?g
+
3O2  2CO2 +
100.0 g
100.0 g C2H5OH
1 mol C2H5OH
3H2O
?g
2 mol CO2
44.01 g CO2 = 191.1 g CO2
46.07 g C2H5OH 1 mol C2H5OH 1 mol CO2