CHAPTER 10
THE MOLE
The mole (mol) is one of the
seven base units in the SI
system.
It measures the amount of
substance.
The form in which a substance
exists is its “representative
particle”.
Representative particles can be
atoms, ions, molecules, formula
units, or anything else.
Units of measure
1 dozen = 12
1 gross = 144
1 ream = 500
1 mole = 6.02 x 1023
The mole is the “chemist’s dozen”.
It is a convenient way to count
extremely large numbers of atoms,
molecules or ions.
Just as one dozen is 12
representative particles,
23
a mole is 6.02 x 10
representative particles.
602,000,000,
000,000,000,
000,000!!!!!
Examples:
1 mole Fe = 6.022 x 1023 atoms of Fe
1 mole H2O molecules = 6.022 x 1023 molecules
of water
1 mole Na+ ions = 6.022 x 1023 Na+ ions
1 mole eggs = 6.022 x 1023 eggs
6.02 X 1023 Watermelon Seeds:
Would be found inside a melon slightly larger than the moon.
6.02 X 1023 Donut Holes:
Would cover the earth and be 5 miles (8 km) deep.
6.02 X 1023 Pennies:
Would make at least 7 stacks that would reach the moon.
6.02 X 1023 Grains of Sand:
Would be more than all of the sand on Miami Beach.
6.02 X 1023 Blood Cells:
Would be more than the total number of
blood cells found in every human on earth.
Review: Diatomic Elements
Certain elements are only stable
in pairs or with other elements in
a compound. These elements
are called the diatomic elements.
There are 7 diatomic elements:
Hydrogen, bromine, oxygen,
nitrogen, chlorine, iodine,
and fluorine
(Memory trick: HOFBrINCl or
Infamous 7)
Avogadro’s Number
6.02 x 1023 is called
Avogadro’s number. It is
named after Amadeo
Avogadro who did work in
the 1800’s that allowed
6.02 x 1023 to be calculated.
Gram atomic mass (gam)
-the average atomic mass of an
element in grams
-mass of one mole of atoms of a
monatomic element
-use the periodic table and take
masses to 0.01 g
Example:
C =12.01 g = mass of 6.022 x
1023atoms
12.01 g/mol is the gram atomic
mass (molar mass) of carbon
Gram molecular mass (gmm)
-mass of one mole of a
molecule
-sum of the atomic masses of
each atom in the molecule
1 mol H2O: 2 mol H
1 mol O
=2 x 1.01 g H/mol =
2.02 g
=1 x 16.00 g O/mol = 16.00 g
18.02 gH2O
#7. What is the gram molecular
mass of CH3OH?
C 1 x 12.01 = 12.01
H 4 x 1.01 = 4.04
O 1 x 16.00 = 16.00
32.05 g
Gram formula mass (gfm)
-mass of one mole of an ionic
compound
-sum of the atomic masses of
each atom in a formula unit
#8. What is the gfm of
magnesium phosphate?
Mg3(PO4)2
3 mol Mg 3 x 24.31 g = 72.93 g
2 mol P 2 x 30.97 g = 61.94 g
8 mol O 8 x 16.00 g =128.00 g
262.87 g
Gram formula mass is a generic
term and can be used for either
ionic or molecular compounds.
Molar mass or molecular
weight are terms also used to
mean the same thing.
Molar mass: aka
•
•
•
•
•
•
Gram formula mass
Gram molar mass
Gram molecular mass
Gram formula weight
Gram atomic mass
Molecular weight
#9. What is the molar mass of
ammonium sulfate?
(NH4)2SO4
2 mol N 2 x 14.01 = 28.02
8 mol H 8 x 1.01 = 8.08
1 mol S 1 x 32.07 = 32.07
4 mol O 4 x 16.00 = 64.00
132.17 g
Stop for now…..