Chemistry Notes
What is a mole?
One Step Problems
A Mole...
A mole is a unit of
measurement that tells how
many particles of something
you have!
1 mole = 6.02 x 1023 particles
What are particles?
Particles could be anything,
but because of the size of the
number, we usually mean
atoms, molecules or formula
units.
Avogadro’s Number
23
10
The number 6.02 x
is
called Avogadro’s number.
Practice Problem #1
How many moles are in
2.57 x 1025 atoms He?
Practice Problem #1
How many moles are in
2.57 x 1025 atoms He?
2.57 x 1025 atoms He x 1 mole He = 42.7 moles He
6.02 x 1023 atoms He
Practice Problem #2
How many molecules of CO2
are in 25.3 moles?
Practice Problem #2
How many molecules of CO2 are
in 25.3 moles?
25.3 moles CO2 x 6.02 x 1023 molecules CO2 = 1.52 x 1025 molecules
1 mole CO2
Moles and Volume
1 mole of all gases at a certain set
of conditions called STP
(standard temperature and
pressure) have the same
volume: 22.4L
So, 1 mole = 22.4L (gas @ STP)
Practice Problem #3
How many moles of O2 are in
29.3L of O2 gas?
Practice Problem #3
How many moles of O2 are in
29.3L of O2 gas?
29.3 L O2 x 1 mole O2 = 1.31 moles O2
22.4 L O2
Practice Problem #4
If you have 3.6 moles of N2O
(Nitrous oxide) how many liters
would you have?
Practice Problem #4
If you have 3.6 moles of N2O
(Nitrous oxide) how many
liters would you have?
3.6 moles N2O x 22.4 L N2O = 81 L N2O
1 mole N2O
Mass and Moles
How do we usually measure
out chemicals in a lab?
We usually use mass to
measure out chemicals.
Mass and Moles
The problem with mass is that
not all atoms or compounds
have the same mass.
Mass and Moles
Avogadro’s number was
established by using Carbon12 as a standard. The
number of particles in 12
grams of carbon 12 was set as
1 mole.
Mass and Moles
The atomic mass on the
periodic table is also an
element’s molar mass (the
mass of one mole of an
element, measured in
g/mol).
What is the molar mass of...
What is the molar mass of...
He
What is the molar mass of...
He 4.0026 g/mol
What is the molar mass of...
He 4.0026 g/mol
Al
What is the molar mass of...
He 4.0026 g/mol
Al 26.982 g/mol
What is the molar mass of...
He 4.0026 g/mol
Al 26.982 g/mol
Ba
What is the molar mass of...
He 4.0026 g/mol
Al 26.982 g/mol
Ba 137.327 g/mol
What is the molar mass of...
He 4.0026 g/mol
Al 26.982 g/mol
Ba 137.327 g/mol
Rn
What is the molar mass of...
He
Al
Ba
Rn
4.0026 g/mol
26.982 g/mol
137.327 g/mol
222 g/mol
Furthermore...
Since compounds are just
atoms bonded together, you
can find the molar mass of a
compound by adding
together the molar mass of all
the elements in the
compound.
What is the molar mass of...
What is the molar mass of...
NaCl
What is the molar mass of...
NaCl
58.443 g/mol
What is the molar mass of...
NaCl
CO2
58.443 g/mol
What is the molar mass of...
NaCl
CO2
58.443 g/mol
44.009 g/mol
What is the molar mass of...
NaCl
CO2
Be3N2
58.443 g/mol
44.009 g/mol
What is the molar mass of...
NaCl
CO2
Be3N2
58.443 g/mol
44.009 g/mol
55.0506 g/mol
What is the molar mass of...
NaCl 58.443 g/mol
CO2
44.009 g/mol
Be3N2 55.0506 g/mol
Ca(NO3)2
What is the molar mass of...
NaCl 58.443 g/mol
CO2
44.009 g/mol
Be3N2 55.0506 g/mol
Ca(NO3)2 164.088 g/mol
Practice Problem #5
How many grams of iron are
in 3.5 moles?
Practice Problem #5
How many grams of iron are
in 3.5 moles?
3.5 moles Fe x 55.847 g Fe = 195.5 g Fe
1 mole Fe
Practice Problem #6
How many moles of Na2O are
in 355.1g?
Practice Problem #6
How many moles of Na2O are
in 355.1g?
355.1 g Na2O x
1 mole Na2O = 5.73 mol Na2O
61.979 g Na2O