CHEMICAL
QUANTITIES
Measuring Matter
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Count
Weigh
Volume
Each of these measurements is related
to a single quantity called the “mole”
The Mole
A mole is a convenient standard
quantity used to count
representative particles.
WHY?
because …. atoms and molecules are
so tiny, chemists use this counting
unit called the mole.
 it represents 6.02 x 1023 molecules or
atoms or particles
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Representative particles:

the type of particle that make up a substance
substance
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elements
Molecular compounds
Ionic compounds
representative particles



atoms
molecules
formula units
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Just as a dozen is always 12, a
mole is always 6.02 x 1023.
This is called Avogadro’s
number because Amedeo
Avogadro came up with the
idea!!
Who is he, you ask?.....
Amedeo Avogadro
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Was a lawyer and
scientist (physics)
In 1811 proposed
that equal volumes
of all gases contain
the same number of
molecules
How many? Good
question!......

The number of
molecules in 1 mole
of gas is known to
be 6.022 x 1023

He was right and so we
now apply this to all
molecules (not just
gases).
The mole is so
important to
chemistry that we
actually have
National Mole Day.
It is every October
23 from 6:02 in the
morning until 6:02 in
the evening.
HOW DO YOU CELEBRATE
MOLE DAY?????
Better ideas……….!
Just imagine….
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If you had a mole of dollars ($6.022 x
1023) and you spent $1 billion every
second of every minute of every hour of
every day for 70 years….
You would have spent less than 1% of
your money! WOW!
Examples
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1 mole of carbon = 6.022 x 1023 C atoms.
1 mole of water = 6.022 x 1023 H2O
molecules.
1 mole of sodium chloride = 6.022 x 1023
NaCl formula units.
1 mole of glucose = 6.022 x 1023 C6H12O6
molecules.
Pretty simple, eh?
Converting from moles to
Representative particles
multiply by 6.022 x 1023
MOLES
divide by 6.022 x 1023
REPRESENTATIVE
PARTICLE
You try it….
How many moles of magnesium are 3.01x
1022 atoms of Mg?
Answer: 3.01x 1022 atoms
6.02 x 1023 atoms/mol
= 0.500 x 10-1
= 5.00 x 10-2 mol Mg
Practice!

Do problems #5 - 8
on page 51-52
If you want the number of atoms
in a mole of a compound…
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you must know how many atoms are in
the compound
Ex: how many atoms are in 1 mole of CO2?
1 mol X
6.022 x 1023 atoms/mol X 3 atoms
= 18.06 x 1023atoms
= 1.81 x 1024atoms
If you want the number of ions in
a mole of a compound…

you must know how many ions are in
the compound

Ex: how many F- ions are in 1.46 mole of AlF3?
1.46 mol
X
6.022 x 1023 formula units/mol X 3 F- ions
= 26.3676 x 1023 F- ions
= 2.64
1024 F- ions
 Do
problems
#9 - 11
On page 52
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Converting from representative
particles reverses the process
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Atoms, molecules, formula units are
divided by Avogadro’s number to get
the number of moles!
How many moles are present in a
sample of 5.83 x 1024 molecules
of CO2 ?

5.83 x 1024 molecules of CO2
6.02 x 1023 molecules /mol
= 0.984 x
101 mol of CO2
9.84 mol of CO2
Turn to page 53
Answer questions
#12-15
New
Stuff……
Representative
Particles
Multiply by
6.02x1023
Divide by
6.02x1023
Moles
Divide by
molar
mass
Multiply
by molar
mass
Mass
Molar Mass
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Molar mass is the mass in grams of
one mole of any element or
compound.
The units for molar mass are g/mol
It can refer to atoms,molecules or
formula units.
Huh?
Molar Mass
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Gram atomic mass……used for elements
Gram molecular mass….used for molecules
Gram formula mass.....used for ionic compounds
All of these can be referred to as
gram formula mass or molar mass
…………..…what?!
Gram Atomic Mass (gam)
is the mass in grams of an atom = 1gam
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Numerically it is equal to its atomic
mass (you know…on the periodic
table!)
Ex: 1mol S = 32.1g = 1gam S
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1mol Hg = 200.6g = 1gam Hg
1mol Fe = 55.8g = 1gam Fe
Example:
Molar mass of carbon (aka gram
atomic mass) is the mass of one
mole of carbon, which would be
12.01 g/mol
(refer to atomic mass of C on periodic
table).
 What would be the molar mass of He?
 What would be the molar mass of Ba?
Gram Molecular Mass (gmm)
is the mass in grams of the atoms which
make up the molecule
Ex:
1mol SO3 = 32.0g + 3(16.0g)
= 80.1g = 1gmm
1mol C6H4Cl2 = 6(12.0g) + 4(1.0g) + 2(35.5g)
= 147.9g = 1gmm
Molar mass of water (aka gram molecular mass)
would be the mass of one mole of
water………. which we find by adding up the
atomic masses of each element in the
molecule.
Molar mass (H2O) = 2 x 1.01 = 2.02
1 x 16.0 = 16.0
18.02g/mol
What is the molar mass of sulfuric acid?
H2SO4 = (2 x 1.01) + 1(32.0) + 4(16.0) =
50.01g/mol
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Gram Formula Mass (gfm)
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is the mass in grams of the ions which
make up the ionic compound
Examples:
1mol potassium iodide (KI)
39.1g + 126.9g = 166.0g = 1gfm KI
1mol ammonium carbonate (NH4)2CO3
2(14.0g) + 8(1.0g) + 12.0g + 3(16.0g)
= 96.0g = 1gfm (NH4)2CO3
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All solids, liquids and gases can be
converted from mass to moles and vice
versa.

From mass to moles: divide by molar mass
From moles to mass: multiply by molar mass

multiply by molar mass
MOLES
MASS
divide by molar mass
EXAMPLE:

What is the mass of 4.2 mol of silver
nitrate?
From moles to mass…… Multiply by molar
mass
Molar mass =
AgNO3 = (107.87) + (14.01) + 3(16.00) = 169.88 g/mol
ANSWER:
Mass = 4.2 mol x 169.88g/mol
= 713.5g
Rasputin! Ever hear of him….?
If his murderers
had calculated the
correct quantity of
potassium cyanide,
they could have
killed him with
much less effort….
HCl + KCN  HCN + KCl
hydrochloric acid
potassium cyanide
hydrocyanic acid
potassiun chloride
However, they would have had to know about his
unique medical condition first…….
HCl + KCN  KCN + HCl
hydrochloric acid
potassium cyanide
KCN  KCN
potassium cyanide
potassium cyanide
potassium cyanide
hydrochloric acid
See……..
chemistry is
useful in
everyday
life!