Molar Mass & The Mole
…..With Some Molar
Conversions
I
II
III
IV
What you will need…..
 Periodic
Table
 Calculator
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Please
What is the Mole?

A counting number (like a dozen)

Avogadro’s number (NA)

1 mole = 6.022  1023 representative
particles (atoms, molecules, formula units, ions, etc)
Molar Mass

Mass of 1 mole of an
element or compound

Atomic mass (on the PT) tells the...
 mass of each atom (amu)
 grams per mole (g/mol)
Molar Mass

Avogadro discovered the
relationship between number of
particles and volume of a gas

This was used to find the
relationship for particles in a mole
Molar Mass Examples

carbon
12.01 g/mol

aluminum
26.98 g/mol

zinc
65.37 g/mol
Molar Mass Examples

water
 H2O
 2(1.008) + 15.999 = 18.02 g/mol

sodium chloride
 NaCl
 22.99 + 35.45
= 58.44 g/mol
Molar Mass Examples

sodium bicarbonate
 NaHCO3
 22.99 + 1.008 + 12.01 + 3(15.999)
= 84.01 g/mol

sucrose
 C12H22O11
 12(12.01) + 22(1.008) + 11(15.999)
= 342.28 g/mol
Molar Conversion Examples
 How
many moles of carbon
atoms are in 26 g of carbon?
26 g C 1 mol C
12.01 g C
= 2.2 mol C
Mole/Particle Conversions
6.022  1023
NA
NUMBER
MOLES
OF
1 Mole
(particles/mol)
NA atoms/mol
NA molecules/mol
PARTICLES
Particles =
atoms,
molecules,
formula units,
ions, etc
Representative Particles & Moles
Substance Chemical Representative Rep Particles
Formula
Particle
in 1.00 mole
Carbon
C
Atom
6.02 x 1023
Nitrogen
gas
N2
Molecule
6.02 x 1023
Calcium ion
Ca2+
Ion
6.02 x 1023
Magnesium
fluoride
MgF2
Molecule
6.02 x 1023
Mole/Particle Conversion Examples
 How
many molecules are in
2.50 moles of C12H22O11?
2.50 mol
C12H22O11
6.02  1023
molecules
C12H22O11
1 mol
C12H22O11
= 1.51  1024
molecules
C12H22O11
Mole/Particle Conversion Examples
you have 2.23 x 1018 atoms of
sodium, how many moles is
that?
 If
2.23  1018 1 mole Na
atoms Na
6.02  1023
atoms Na
3.70 x 10-6
= moles Na
Mole/Particle Conversion Examples
 How
many molecule are 3.75
moles of calcium hydroxide?
6.02  1023
3.75
molecules
mol Ca(OH)2 Ca(OH)2
= 2.26  1024
1 mol Ca(OH)2 molecules
Ca(OH)2
Molar Conversions
6.02  1023
NA
molar
mass
MASS
NUMBER
MOLES
IN
GRAMS
(g/mol)
OF
(particles/mol)
PARTICLES
Particles = atoms,
molecules, formula
units, ions, etc
NA atoms/mol
NA molecules/mol
Molar Conversion Examples
the mass of 2.1  1024
molecules of NaHCO3.
2.1  1024
84.01 g
Molecules 1 mol
NaHCO3
NaHCO3
NaHCO3
 Find
6.02  1023 1 mol
Molecules
NaHCO3
NaHCO3
= 290 g NaHCO3
Molar Conversion Examples
 How
many atoms are in 22.5
grams of potassium?
22.5 g K
1 mol K
6.02  1023
atoms K
39.10 g K 1 mol K
= 3.46 x 1023 atoms K
Gases
•Many of the chemicals we deal with
are gases.
•They are difficult to weigh.
•Need to know how many moles of gas
we have?
•Two things effect the volume of a gas
• Temperature and Pressure
•Compare at the same temp. and
pressure
Standard Temperature and Pressure
0ºC and 1 atm pressure
abbreviated STP
At STP 1 mole of gas occupies 22.4 L
Called the molar volume
Avogadro’s Hypothesis - at the same
temperature and pressure equal
volumes of gas have the same number
of particles.
Molar Volume
Avogadro's Theory: Two gases
containing equal numbers of molecules
occupy equal volumes under similar
conditions.
Standard Temperature and Pressure:
0 oC and 1 atm
Molar Volume at STP = 22.4 L
Mole Calculations

What is the mass of 3.36 L of
ozone gas, O3, at STP?
3.36 L O3
1 mol O3
48 grams
of O3
22.4 L O3 1 mol O3
= 7.2 grams of O3
Mole Calculations

How many molecules of hydrogen
gas, H2, occupy 0.500 L at STP?
0.50 L H2
1 mol H2
6.02  1023
molecules of H2
22.4 L H2
1 mol H2
= 1.34 x 1022 molecules H2
Mole Ratios






The ratio of the moles of one molecule to the
atoms within that molecule.
molecular formulas give atom-to-atom and moleto-mole ratios
 example: molecular formula C6H12O6
atom-to-atom ratios atom-to-molecule ratios
6 atoms C
12 atoms H
6 atoms C
6 atoms O
12 atoms H
6 atoms O



6 atoms C
1 molecule
12 atoms H
1 molecule
6 atoms O
1 molecule
Mole Ratios
Example: molecular formula C6H12O6
mole-to-mole ratios
(elements)
6 mol C
12 mol H
6 mol C
6 mol O
12 mol H
6 mol O
mole-to-mole ratios
(compound)
6 mol C
1 mol C6H12O6
12 mol H
1 mol C6H12O6
6 mol O
1 mol C6H12O6
problems that ask you to relate one substance to
another require mole-to-mole ratios