Chapter 8

Factor Label Method and the Mole

What is Avogadro’s Favorite Novel?

What is Avogadro’s Favorite Novel?

Molby Molby DickDick

A ratio is an equality is a conversion factor.

• Density of Aluminum = 2.7 g/cm3

• Land speed record = 763 miles/hr

• 1.61 km = 1 mile

• 1 pound = 0.4536 kilograms

What Do We Know About the Mole

What Do We Know About the Mole

• 1 mol = 6.02 x 1023

What Do We Know About the Mole

• 1 mol = 6.02 x 1023

• Any equality or ratio can be made into a conversion factor and then used to solve problems with the factor label method.

6.02 x 1023 “particles”

1 mole

or

1 mole

6.02 x 1023 “particles”

Note that particles could be atoms, molecules,

formula units, ions, etc.

Avogadro’s Number as a Avogadro’s Number as a Conversion FactorConversion Factor

= 6.02 x 1023 C atoms

= 6.02 x 1023 H2O molecules

= 6.02 x 1023 NaCl “molecules”

(technically, ionic compounds

are not molecules, they are called

formula units)

A Mole of ParticlesA Mole of Particles Contains 6.02 x 1023 particles

1 mole C

1 mole H2O

1 mole NaCl

What Do We Know About the Mole

What Do We Know About the Mole

• 1 mol of any substance = it’s gfm

What’s in a Name?What’s in a Name?• Atomic Mass/Atomic Weight/Molecular Mass/Molecular

Weight/Formula Mass/Formula Weight: If you have a single atom or

molecule or compound, mass is measured in amu’s.

• Gram Atomic Mass/Gram Atomic Weight/Gram Molecular Mass/Gram

Molecular Weight/Gram Formula Mass/Gram Formula Weight/Molar

Mass: If you have a mole of atoms or molecules or a compound, mass is

measured in grams.

• But, the numerical value is the same whether you have 1 mole or one

particle. Only the units are different. (This is the beauty of Avogadro’s

Number!).

• THE POINT: You may hear all of these terms which mean the

SAME NUMBER… just different units.

• Equal to the atomic mass (get from

chart)

• The mass of 1 mole (in grams)

• 1 mole of C atoms = 12.0 g

Gram Atomic Mass (Molar Mass) of Gram Atomic Mass (Molar Mass) of an atom an atom

1 mole of Mg atoms

Gram Atomic Mass (Molar Mass) of Gram Atomic Mass (Molar Mass) of an atom an atom

24.3 g

1 mole of Cu atoms

Gram Atomic Mass (Molar Mass) of Gram Atomic Mass (Molar Mass) of an atom an atom

63.5 g

Gram Formula Mass (Molar Mass) Gram Formula Mass (Molar Mass) of Molecules and Compoundsof Molecules and Compounds

• Mass in grams of 1 mole

• Equal to the formula mass (sum of the atomic masses) expressed in grams

Gram Formula Mass (Molar Mass) Gram Formula Mass (Molar Mass) of Molecules and Compoundsof Molecules and Compounds

• Mass in grams of 1 mole • Equal to the formula mass (sum of the atomic

masses) expressed in grams

Gram Formula Mass of Ca3(PO4)2

• 3 x 40.1 = 120.3• 2 x 31.0 = 62.0• 8 x 16.0 = 128.0

= 310.3 g/mol

Gram Formula Mass (Molar Mass) Gram Formula Mass (Molar Mass) of Molecules and Compoundsof Molecules and Compounds

List “2” things you know about a mole of H.

• 1 mole H = 6.02 x 1023 H atoms

• 1 mole H = 1.0g

• What could we use these equalities to do in a factor label problem?

List “2” things you know about a mole of H2O

• 1 mole H2O = 6.02 x 1023 H2O molecules

• 1 mole H2O = 18.0g

List “2” things you know about a mole of Na2O

• 1 mole Na2O = 6.02 x 1023 Na2O formula units

• 1 mole Na2O = 62.0g