THE MOLE
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Not these kinds of moles, but…
The Science Mole
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The “mole” is just a number, the
same way a “dozen” is 12 of
something….
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A dozen eggs = 12 eggs
A dozen people = 12 people but 2
dozen (24) legs
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The mole is much MUCH larger
than a dozen.
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1 dozen = 12
1 mole = 6.02 X 1023
A Mole is the amount of substance that
contains 6.02 x 1023 (Avogadro’s #)
particles of that substance
The mass of a mole of any element or
compound is called its molar mass.
mass of a substance (g)
molar mass of substance (g/mol)
TO FIND MOLAR
MASS OF
SUBSTANCE
add up the molar masses
of the elements shown
in the formula
1. H2O (water)
2. KNO3 (potassium nitrate)
Hydrogen =
1.0g/mol x 2
Potassium (K)= 39.1g/mol x 1
Oxygen
16 g/mol x 1
Nitrogen (N)
=
Molar Mass = 18 g/mol
Oxygen (O)
= 14 g/mol x 1
= 16g/mol x 3
Molar mass = 101.1 g/mol
THEREFORE: 1 mole of water has a molar mass of 18g/mol and 1
mole of potassium nitrate has a molar mass of 101.1g/mol.
What is the molar mass of NaCl?
Na =
1 x 23g/mol
= 23
Cl =
1 x 35.5 g/mol
= 35.5
58.5 g/mol
What is the molar mass of (NH4)2SO4
N = 2 x 14 g/mol
= 28
H = 8 x 1 g/mol
=
S = 1 x 32 g/mol
= 32
O = 4 x 16 g/mol
= 64
8
132 g/mol
mass of a substance (g)
molar mass of substance (g/mol)
convert
How many moles of hydrochloric acid
are in 100 grams of hydrochloric acid
(HCl)?
n (# of moles)= grams
molar mass
n=?
g = 100
n = 100 g
Molar Mass = 36.5g/mol
36.5g/mol
Hydrogen
1g/mol x 1
Chlorine
35.5 g/mol x 1
molar mass = 36.5 g/mol
n = 2.74 mol
How many grams are in 11.1
moles of water (H20)?
n (# of moles)= grams
molar mass
n = 11.1 moles
g=
Molar Mass = 18 g/mol
11.1 moles = _____
18 g/mol
Hydrogen
1 g/mol x 2
Oxygen
16 g/mol x 1
molar mass = 18 g/mol
g = 200 grams
What is the mass of 0.42
moles of potassium nitrate
(KNO3)?
n(moles) =
0.42 moles
Molar Mass = 101.1 g/mole
n (# of moles)= grams
molar mass
g=?
0.42 mole = __g__
K=
39.1 g/mole
N=
14 g/mole
0 = 16 g/mole
X3=
48g/mole
101.1 g/mole
101.1 g/mole
g = 42.46 grams
o The mass of a mole of any element or compound is called
its molar mass.
1. H2O (water)
Hydrogen =
1.0g/mol x 2
Oxygen
16 g/mol x 1
=
Molar Mass = 18 g/mol
o A Mole is the amount of substance that contains
6.02 x 1023 (Avogadro’s #) particles of that substance
o Formula to convert between moles and mass (g) is:
n (# of moles)= grams
molar mass
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Study guide, Module 3, page 11 and
18
436 WORKSHEET # 2