A Chemist’s “Dozen”
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The particles that make up matter (ions,
atoms, and molecules) are extremely small
Only large amounts of these particles can be
weighed. In order to simplify these large
numbers we use the mole
 1Mole = 6.022 x 1023 particles
▪ Particles can be atoms, molecules, ion, bananas,
lollipops, etc.
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1Mole = 6.022 x 1023 particles
 Particles can be atoms, molecules, ion, bananas
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6.022 x 1023 is known as Avogadro’s Number
Amedeo Avagadro
1776-1856
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How does the mole get this specific value?
 The value of the mole is equal to the number of
atoms in exactly 12 grams of pure carbon-12.
▪ 12g C = 1 mole C atoms = 6.022 x 1023 C atoms
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This definition gives a relationship between
mass (grams) and the number of atoms
(Avagadro’s number)
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A Road Map
Grams
Remember: The Molar Mass is
the sum of the weights of each
element in the compound. NH3
would be 1(14)+3(1)= 17 g/mol
Atoms
Mole
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E.g. How many atoms are in one mole of
pennies?
Avagadro’s Number
1 mole pennies
6.022 x 1023 pennies = 6.022 x 1023 pennies
1 mole pennies
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E.g. How many grams are in 1 mole of
sodium?
1 mol Na
23 g Na
1 mol Na
= 23 grams sodium
This is the
Gram Formula Mass
(gfm) ratio
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E.g. How many molecules are in 13 grams of
H2SO4?
 Solve in two steps.
Avagadro’s
Number
13 g H2SO4 1 mol H2SO4 6.022 x 1023 molecules H2SO4 =
98 g H2SO4
1 mol H2SO4
Gfm
= 7.988 x 1022 molecules H2SO4
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E.g. How many moles are in 31 atoms of
copper?
31 atoms
1 mol = 5.148 x 10-23 moles copper
6.022 x 1023
Avagadro’s Number
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