Download THE MOLE - Laureate International College

THE MOLE
... a unit of counting
Quantities in Chemical Reactions
Big Ideas

Relationships in chemical reactions can be
described quantitatively

The efficiency of chemical reactions can be
determined and optimized by applying an
understanding of quantitative relationships
in such reactions.
How Scientists Keep Track of Atoms
• One way to measure how much of
a substance is available is to count
the # of particles in that sample
• However, atoms & molecules are
extremely small
• To solve this problem, scientists
developed the concept of the mole
• SYMBOL IS n .
•*The mole is a unit song
The Mole
A dozen donuts = 12
 A mole of donuts = 6.023x1023

a dozen shoes = 12
 A mole of shoes = 6.023x1023

1 mole = 6.02 x 1023 entities of a
substance
 1 mole of anything = 6.023x1023
= 602,000,000,000,000,000,000,000!!!

WHAT IS THE MOLE?
FYI….
A formula unit is
a term used to
represent the
lowest whole
number ratio of
ions in an ionic
compound.
Different types of particles include:
atoms OR molecules OR ions OR
electrons OR formula units, etc.
Avogadro’s Constant = NA
= 6.023 x 1023 particles
1 mol
Units of moles are mol
On your calculator:
EE or EXP or x10^
WHERE DID THIS NUMBER
COME FROM?
A mole is the amount of substance
that contains as many particles as
exactly 12.000g of Carbon-12
The Mole- Examples

1 mole of carbon contains 6.02 x
1023 atoms of carbon

1 mole of H2O contains 6.02 x 1023
molecules of H2O

1 mole of NaCl contains 6.02 x 1023
formula units of NaCl
How Big is Avogadro’s
Number?
If you had one mole of dollars,
how long would it take to spend it
at a rate of $1,000,000 per day?
◦
o
6.02 x 1023 ÷ 1,000,000 = 6.02 x 1017 d
6.02 x 1017 d ÷ 365 d/a = 1.65 x 1015 a
Put this into perspective…
o The sun is about 4.6 x 109 years old and will burn out in
about 5 x 109 years.
o You will need to spend faster!!
The mole is a BIG number.

The green pea analogy puts it into
perspective as well:

Did you know that 12 pencils will contain
a mole of carbon atoms?
Variables to Know
N
•
•
•
n = number of moles
n
NA
N = number of particles
NA = Avogadro’s number (6.02 × 1023)
•
Two possible types of questions:
o
Moles to Particles

o
N = n x NA
Particles to Moles

n = N / NA
Using Avogadro’s Constant
•
•
How many atoms in 2
moles of carbon?
N = n x NA
= 2 moles x (6.02 x
1023)
= 1.2 x 1024 particles
of C
How many moles is 5.0 x
1024 particles of iron?
n = N / NA
= 5.0 x 1024/6.02 x
1023
= 8.3 moles of Fe
•
How many atoms in 2 moles of
water?
N = n x NA
= 2 moles x 6.02 x 1023
= 1.2 x 1024 molecules of
H2O
= 3 atoms per molecule
= 3 x (1.2 x 1024 )
= 3.6 x 1024 atoms in 2
moles of H2O
LEARNING CHECK (round to 3 sig. figs.)
 How many molecules of CO2 are in
4.56 moles of CO2? 2.75 x 10 molecules
 How many moles of water is 5.87 x
1022 molecules? 0.0975 mol (or 9.75 x 10 )
 How many moles is 7.7812.9xmoles
1024
formula units of MgCl2
 How many atoms of carbon are in
1.23 mol of C6H12O6? 4.44 x 10 atoms C
24
-2
24
Mass to Mole Calculations

Atomic Mass
◦ Mass of one atom
◦ Unit μ = atomic mass unit = a.m.u
 Eg. Each hydrogen atom has a mass of 1.001μ
◦ 1 μ equals approximately 1.67 x 10-24g, which
is extremely small and not practical to measure.

Enter Molar Mass….
Molar Mass (MM)

The mass of 1 mole of a substance

Mass of 6.023 x 1023 particles

Units are g/mol
◦ Eg. The molar mass of Hydrogen is 1.01 g/mol
Molar Mass

Molar mass and atomic mass have the
same numbers except there is a unit
difference.
Atomic Mass

Molar Mass
Li
6.94 μ/atom
6.94 g/mol
Ag
107.86 μ/atom
107.86 g/mol
The g/mol unit is more useful that μ
because…
It can be measured in the lab using a scale
Example

Eg. Find the molar mass of water:
H2O
H: 2 x 1.001g/mol
O: 1 x 16.00 g/mol
18.002g/mol
Eg. Find the molar mass of calcium
phosphate:
Ca3(PO4)2
Ca: 3 x 40.08
g/mol
P:
2 x 30.97 g/mol
O: 8 x 16.00 g/mol
310.2g/mol

The same as:
Gram Molecular Mass (for molecules)
Gram Formula Mass (ionic
compounds)
 Gram Atomic Mass (for elements)
 molar mass is just a much broader
term than these other specific masses
Mole Calculations
MM = m/n
m
n = m/MM
MM
n
m = MMn
N = nNA
n = N/NA
HOMEWORK
Complete Moles
Worksheet. Try all
questions to the
best of your ability.
Good luck!