STOICHIOMETRY
CHEMISTRY
MS. MATTSON
STOICHIOMETRY
• Stoichiometry
• the mole-mass relationship between reactants
and products.
• Molecular Mass
• measured in atomic mass units (a.m.u.)
• Review: Calculate the molecular mass of
chloroethane C2H5Cl.
• 64.5 a.m.u.
STOICHIOMETRY
• Mole
• A unit that refers to the number of molecules or
ions that take part in a chemical reaction.
• Molar Mass
• One mole is equal to the molecular mass in
grams.
• Ex: C2H5Cl = 64.5 a.m.u. = 1 mole = 64.5 grams
• Potassium (K) has molecular mass 39.1 a.m.u.
• What is 1 mole of potassium in grams?
• 39.1 grams
STOICHIOMETRY
• Molecular Mass (a.m.u.) = Molar Mass (g) = 1 mole
• Activity 1
• Given molecule A in grams show the equation
that would convert grams of A to moles of A.
• Given the moles of molecule B show the equation
that would convert moles of B to grams of B.
STOICHIOMETRY
• Problem 1
• Convert 15.0 grams of C2H4 to moles of C2H4.
• 0.536 moles
• Convert 0.536 moles of HCl to grams of HCl.
• 19.6 grams
STOICHIOMETRY
• Molecular Mass (a.m.u.) = Molar Mass (g) = 1 mole
• Activity 2
• Given the reaction 2A + 3B  A2B + B2
show
the equation that would convert the grams of A
into the grams of B that are required to fulfill the
reaction.
• Grams to moles to moles to grams! 
STOICHIOMETRY
• Problem 2
• Sodium hypochlorite (NaOCl) is best known as
household bleach. It is prepared by reacting
sodium hydroxide (NaOH) with chlorine Cl2:
2NaOH + Cl2  NaOCl + NaCl + H2O
• How many grams of NaOH are needed to react
with 25.0 g of Cl2?
• 28.2 g NaOH
STOICHIOMETRY
• Problem 3
• Aspirin is prepared by a reaction of salicylic acid
(C7H6O3) with acetic anhydride (C4H6O3) according
to the following equation:
C7H6O3 + C4H6O3

C9H8O4 + CH3COOH
Salicylic acid Acetic anhydride
Aspirin
138.1 g
102.1 g
180.2 g
• How many grams of acetic anhydride are needed to
react with 4.50 g of salicylic acid?
• 3.33 g C7H6O3
• How many grams of aspirin will result?
• 5.87 g C9H8O4
STOICHIOMETRY
• Problem 4
• In preparation of iron from hematite Fe2O3 reacts
with carbon:
Fe2O3 + C  Fe + CO2
How many grams of carbon are needed to react
with 525 g of hematite?
59.2 g C
STOICHIOMETRY
• Problem 5
Magnesium metal burns in oxygen to form magnesium oxide,
MgO2. Write and balance an equation for this reaction.
2Mg + O2  2MgO2
How many grams of Mg(MM 24.3g) are needed to react with
25.0 g of O2 (MM 32.0g)?
38.0g Mg
How many grams of MgO2 (MM 40.3) will result?
63.0 g MgO2
How many grams of O2 are needed to react with 25.0 g of
Mg?
16.5 g O2
How many grams of MgO2 will result?
41.5 g MgO2