The MoleUnit 7: Stoichiometry – Part I
Mrs. Callender
Lesson Essential Questions
What is a mole?
What is a mole used for?
Atoms are really, really small……
We can not work with individual atoms or AMU’s in the lab. Atomic Mass
Unit WHY?Because we can’t see
things that small!
We as scientists work with portions of matter large enough for us to SEE and MASS on a balance using units of……GRAMS
This presents a problem…..
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A pile of atoms large enough for us to see
contains billions of
atoms.Copper (II)
Sulfate
So how would we keep track of that many atoms?
Chemists came up with a new unit.
The
MOLE
Equivalents or Conversion Factors
1 dozen eggs = 12 eggs
1 rooster = two legs
1 ream of paper = 500 pieces of paper
Equivalents or Conversion Factors
1 mole = 6.02 x 1023
There are EXACTLY 12 grams of Carbon-12 in 1 mole of Carbon-12.
Avogadro’s Number
6.02 x 1023
He studied gases and discovered that no
matter what the gas, there were the same number of molecules
present.Named in honor of Amadeo Avogadro.
1776 - 1856
I did not discover the
number. It was just named after
me.
Units for Avogadro’s Number
1 mole = 6.02 x 1023 (many different units)For instance:
1 mole of pennies = 6.02 x 1023
pennies.This amount is equivalent to 7 stacks of pennies from the Earth to the moon.
Units for Avogadro’s Number
1 mole Mg= 6.02 x 1023 atoms.
1 mole NaCl= 6.02 x 1023
molecules.1 mole Cl2 = 6.02 x 1023
molecules.1 mole SO4
-2 = 6.02 x 1023 ions.
Remem
ber:
HO
FBrINCl
Calculating Formula Mass
Calculate the formula mass of NaCl.
6Na
22.9897
17Cl
35.453
22.99 g + 35.45 g = 58.44 g Therefore, 1 mole of NaCl (6.02
x 1023 molecules) has a mass of 58.44 g
Calculating Formula Mass
Calculate the formula mass of K2O.
19K
39.0983
6O
15.9994
2(39.10) g + 16.00 g = 94.2 g Therefore, 1 mole of K2O (6.02 x
1023 molecules) has a mass of 94.2 g
Calculating Formula Mass
Calculate the formula mass of (NH4)2SO4.7
N14.00
67
6O
15.9994
2(14.01) g + 8(1.01) g + (32.01) + 4(16.00) g = 132.11 g
Therefore, 1 mole of (NH4)2SO4 (6.02 x 1023 molecules) has a mass of 132.11 g
1H
1.00794
16S
32.066
Calculating Formula MassCalculate the formula mass of
CuSO4
5 H2O.29Cu
63.546
6O
15.9994
63.55 g + 32.01g + 4(16.00) g + 5[2(1.01)+16.00] = 249.56 g
1H
1.00794
16S
32.066
.
Therefore, 1 mole of CuSO4 5 H2O (6.02 x 1023 molecules)
has a mass of 249.56 g
.
This type of formula is called a hydrate. It is a salt with water physically attached to it.Example: A salt container with rice intermixed.Since the water is physically attached how
could it be removed?
By heating. When the water is removed the remaining salt is called anhydrous.
