Stoichiometry:
Molar Conversions
What is the Mole?
• A counting number (like a dozen)
• Avogadro’s number
• 1 mole = 6.02  1023 items
How Much is a Mole?
1 mole of hockey pucks would
equal the mass of the moon!
1 mole of basketballs would fill a
bag the size of the earth!
Molar Mass:
the mass of 1 mole of a substance (element or compound)
11
Na
22.989707
Atomic mass tells the:
atomic mass units per atom (amu)
grams per mole (g/mol)
Round to 2 decimal places
There are 12
particles in the nucleus of a
Carbon atom.
The mass of 1 atom of Carbon = 12
amu
The mass of 602,200,000,000,000,000,000,000
atoms of Carbon = 12
grams
Molar Mass of Atoms
Lithium
6.94 g/mol
Aluminum
26.98 g/mol
Cesium
132.91 g/mol
Molar Mass of Compounds
H2O
2(1.01) + 16.00 = 18.02 g/mol
NaCl
22.99 + 35.45 = 58.44 g/mol
Molar Mass Examples
NaHCO3
22.99 + 1.01 + 12.01 + 3(16.00)
= 84.01 g/mol
C12H22O11
12(12.01) + 22(1.01) + 11(16.00)
= 342.34 g/mol
Molar Conversions
molar
mass
6.02  1023
NUMBER
MASS
MOLES
IN
OF
PARTICLES
GRAMS
(g/mol)
(particles/mol)
When to Use Molar Mass (from chart):
When converting the same substance from
• g  mol
• mol g
REMEMBER:
• Mass Number= number grams in 1 mole of the
substance
• Can use mol/g or g/mol
Practice Problem #1
How many moles of carbon are in
26 g of carbon?
26 g C 1 mol C
12.01 g C
= 2.2 mol C
Practice Problem #2
How many grams of carbon are in
5moles of carbon?
5 mol C 12.01 g C
1mol C
= 60g C
Practice Problem #3
How many moles of CO2 are in
26 g of CO2?
26 g CO2 1 mol CO2
=.59 mol CO2
44.01 g CO2
Practice Problem #4
How many grams of CO2 are in
3 mol of CO2?
3 mol CO2 44 g CO2
1 mol CO2
=132 g CO2
Molar Conversions
molar
mass
6.02  1023
NUMBER
MASS
MOLES
IN
OF
PARTICLES
GRAMS
(g/mol)
(particles/mol)
When to Use Avogadro's Number:
When converting the same substance from
•
•
•
•
g  number of particles
number of particles  g
mol number of particles
Number of particles  mol
REMEMBER:
• Avogadro's Number = 6.022 x 1023
• Can use mol/particles or particles/mol
Practice Problem #1
How many molecules are in
2.50 moles of C12H22O11?
6.02  1023
2.50 mol molecules
1 mol
= 1.51  1024
molecules
C12H22O11
Practice Problem #2
Find the mass of 2.1  1024
molecules of NaHCO3.
2.1  1024
molecules
1 mol
84.01 g
6.02  1023 1 mol
molecules
= 290 g NaHCO3
When to Use Mole Ratio (from equation):
When converting from one substance to another
REMEMBER:
• Coefficient tells you the number of moles of each
sustance
Practice Problem #1
2NaClO3  2NaCl + 3O2
How many moles of O2 can be produced from 12.00 moles of NaClO3?
12 mol NaClO3
3 mol O2
2 mol NaClO3
= 18 mol O2
Practice Problem #2
2NaClO3  2NaCl + 3O2
How many moles of NaCl can be produced from 10.00 moles of
NaClO3?
10 mol NaClO3
2 mol NaCl
2 mol NaClO3
= 10 mol NaCl
Practice Problem #3
KOH + HCl KBr + H2O
If you start with 10 grams of potassium hydroxide, how many grams of
potassium bromide can be made?
Molar Mass
10 g KOH 1 mol KOH
Mole Ratio
Molar Mass
1 mol KBr 119 g KBr
56.11 g KOH 1 mol KOH 1 mol KBr
= 21.21 g KBr
Practice Problem #4
Si2H4 + 3O2 2SiO2+ 2H2O
If you start with 45 grams of Si2H4, how many grams of SiO2 can be
made?
45 g Si2H41 mol Si2H4 2 mol SiO2 60.09g SiO2
60.22 g Si2H41 mol Si2H41 mol SiO2
= 89.81g SiO2