For Review
113
Solving a Stoichiometry Problem Involving Masses of Reactants and Products
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Write and balance the equation for the reaction.
Convert the known masses of substances to moles.
Determine which reactant is limiting.
Using the amount of the limiting reactant and the appropriate mole ratios,
compute the number of moles of the desired product.
Convert from moles to grams, using the molar mass.
This process is summarized in the diagram below:
Balanced chemical
equation
Find appropriate
mole ratio
Moles desired substance
Moles limiting reactant
Masses of
known substances
Convert
to moles
Moles of
known substances
Mass of
desired product
Convert
to grams
Find limiting
reactant
Moles limiting
reactant
Key Terms
chemical stoichiometry
Section 3.2
mass spectrometer
average atomic mass
Section 3.3
mole
Avogadro’s number
Section 3.4
molar mass
Section 3.5
mass percent
Section 3.6
empirical formula
molecular formula
Use mole ratio
to convert
Moles of
desired product
For Review
Stoichiometry
䊉 Deals with the amounts of substances consumed and/or produced in a chemical reaction.
䊉 We count atoms by measuring the mass of the sample.
䊉 To relate mass and the number of atoms, the average atomic mass is required.
Mole
12
䊉 The amount of carbon atoms in exactly 12 g of pure
C
23
䊉 6.022 10
units of a substance
䊉 The mass of one mole of an element the atomic mass in grams
Molar mass
䊉 Mass (g) of one mole of a compound or element
䊉 Obtained for a compound by finding the sum of the average masses of its constituent
atoms