Learning Goals
0 Recognize the mole relationships shown by a
chemical formula.
0 Calculate the molar mass of a compound.
0 Convert between the number of moles and
mass of a compound.
0 Apply conversion factors to determine the
number of atoms or ions in a known mass of a
compound.
Chemical Formulas and the Mole
0 Chemical formulas indicate the numbers
and types of atoms contained in one unit
of the compound.
Chemical Formulas and the Mole
0 One mole of CCl2F2 contains one mole of C
atoms, two moles of Cl atoms, and two
moles of F atoms.
Practice
0 Determine the number of moles of Cl- ions
in 2.50 mol of zinc chloride.
Practice
0 How many moles of oxygen atoms are
present in 5.00 mol of diphosphorus
pentoxide?
The Molar Mass of Compounds
0 The molar mass of a compound equals the
molar mass of each element, multiplied by the
moles of that element in the chemical formula,
added together.
0 The molar mass of a compound demonstrates
the law of conservation of mass.
Practice
0 Determine the molar mass of hydrogen
cyanide.
Practice
0 Determine the molar mass of calcium
chloride.
Converting Moles to Mass
0 For elements, the conversion factor is the
molar mass of the compound.
0 The procedure is the same for compounds,
except that you must first calculate the
molar mass of the compound.
Practice
0 What is the mass of 3.25 mol of sulfuric
acid?
Converting Mass to Moles
0 The conversion factor is the inverse of the
molar mass of the compound.
Practice
0 Determine the number of moles present in
35.0 g of hydrochloric acid.
Converting Mass to Particles
0 Convert mass to moles of compound with
the inverse of molar mass.
0 Convert moles to particles with Avogadro’s
number.
Practice
0 A sample of sodium sulfite has a mass of
2.25 g.
0 How many sodium ions are present?
0 How many sulfite ions are present?
0 What is the mass in grams of one formula unit
of sodium sulfite?