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The Mole:
A Measurement of Matter
Prentice-Hall Chapter 10.1
Dr. Yager
Objectives

Describe methods of measuring the amount
of something

Define Avogadro’s number as it relates to a
mole of a substance

Distinguish between the atomic mass of an
element and its molar mass

Describe how mass of a mole of a compound
is calculated
You often measure the amount of something
by one of three different methods — by count,
by mass, and by volume.
The Mole

A mole is the SI unit of counting

A mole equals 6.02 x 1023 of anything

602,000,000,000,000,000,000,000
Avogadro’s Number

Average atomic mass (amu) is equal to
molar mass, the mass of one mole of a
substance.

Formula weight and molecular weight
are the mass of one mole of an ionic and
molecular compound, respectively.
The Other Mole
A mole of any substance contains
Avogadro’s number of representative
particles, or 6.02  1023 representative
particles.
The term representative particle refers to
the species present in a substance: usually
atoms, molecules, or formula units.
Mole Examples
1 mole of “Vanadium” = 6.02 x1023 atoms
50.941 g of “Vanadium” = 6.02 x1023 atoms
1 mole of “Vanadium” = 50.941 g
1 mole of “Helium” = 6.02 x1023 atoms
4.0026 g of “Helium” = 6.02 x1023 atoms
1 mole of “Helium” = 4.0026 g
# of moles = (2.17 x1023 particles) / (6.02 x 1023
particles/mol)
= 0.360 moles
Moles to Number of Particles
# of “S” atoms = (1.14 mol)(6.02 x 1023 atom/mol)
= 6.86 x 1023 atoms
# of “O” atoms = 3 x (1.14 mol)(6.02 x 1023 atom/mol)
= 20.6 x 1023 atoms
Total = 6.86 x 1023 + 20.6 x 1023 = 2.75 x 1024 atoms
Mass of a Mole of an Element
Molar mass is the mass of one mole of
an element, expressed in grams/mol.
You can find the molar mass of an
element under its atomic symbol on the
periodic table.
The molar mass of carbon, sulfur, mercury, and iron
are shown.
Converting Grams to Moles
If given grams, divide by average atomic mass to
get moles:
15 g of “Mo” = 15 g/95.94 g/mole = 0.156 moles
15 g of “H” = 15 g/1.0079 g/mole = 14.88 moles
Mass of a Mole of a Compound
To calculate the molar mass of a compound:
1) find the number of grams of each element
in one mole of the compound.
2) then add the masses of the elements in
the compound.
Use values of molar mass (g/mol) for each
element from the periodic chart.
Thus 1 mol of SO3 has a mass of 80.1 g.
Molar Masses of Glucose, Water,
and Paradichlorobenzene
P = 30.97 g/mole
Cl = 35.45 g/mole
Molar Mass = 30.97 g + 3 x 35.45 g = 137.33 g
1. Three common ways of measuring the
amount of something are by count, by
mass, and
a) by temperature.
b) by volume.
c) by area.
d) by density.
1. Three common ways of measuring the
amount of something are by count, by
mass, and
a) by temperature.
b) by volume.
c) by area.
d) by density.
2. A mole of hydrogen gas, H2(g), contains
6.02 x 1023
a) molecules.
b) atoms.
c) amu.
d) grams.
2. A mole of hydrogen gas, H2(g), contains
6.02 x 1023
a) molecules.
b) atoms.
c) amu.
d) grams.
3. The atomic mass of fluorine is 19.0 amu,
so the molar mass is
a) 19.0 amu.
b) 19.0 g.
c) 6.02 x 1023 amu.
d) 6.02 x 1023 g.
3. The atomic mass of fluorine is 19.0 amu,
so the molar mass is
a) 19.0 amu.
b) 19.0 g.
c) 6.02 x 1023 amu.
d) 6.02 x 1023 g.
4. Calculate the molar mass of ammonium
nitrate.
a) 45.02 g
b) 80.05 g
c) 60.06 g
d) 48.05 g
4. Calculate the molar mass of ammonium
nitrate.
a) 45.02 g
b) 80.05 g
c) 60.06 g
d) 48.05 g