Mole Conversions

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Chemistry 20
Mole Conversions
What is a Mole?
• A term of measurement
• A counting number
–Similar to saying 1 dozen = 12 things
• Avogadro's Number (NA)
= 1 mole
6.02 x 1023 items
A VERY LARGE NUMBER!!!
• 3.00 moles of little green peas would
cover 250 planets the size of Earth
1m deep in green peas
• 1.00 mole of basketballs would fill a
bag the size of the Earth
Mole Conversions
Molar Mass
Mass
In
Grams
Moles
g/mol
Molar Mass
• Molar mass is the mass of one mole in an
element or compound
• Atomic mass tells us that the units are
grams per mole g/mol
Examples:
Carbon, C = 12.01 g/mol
Phosphorus, P = 30.97 g/mol
Molar Mass Examples
What is the Molar Mass of:
Salt, NaCl:
Na = 22.99g/mol
Cl = 35.45g/mol
NaCl = 22.99g/mol + 35.45g/mol = 58.44g/mol
Glucose, C6H12O6:
C6 = 6(12.01g/mol) H12 = 12(1.01g/mol) O6 = 6(16.00g/mol)
C6H12O6 = 6(12.01g/mol) +12(1.01g/mol) 6(16.00g/mol)
= 180.18 g/mol
Sodium bicarbonate, NaHCO3:
Na= 22.99g/mol H=1.01g/mol
O = 3(16.00g/mol)
C=12.01g/mol
NaHCO3= 22.99g/mol + 1.01g/mol + 12.01g/mol + 3(16.00g/mol)
= 84.01g/mol
Mole Conversion Examples
A grade eleven chemistry student has 3.00 g of
boron tribromide (BBr3). How many moles of BBr3
is this?
Molar mass of BBr3 = 10.81 + 3(79.90) = 250.51g/mol
3.00g BBr3 x
1mole
250.51g
= 0.0120 mole BBr3
REMEMBER SIG FIGS!
If I have 50.0g of calcium chlorate Ca(ClO3)2 how
many moles do I have?
Molar Mass Ca(ClO3)2 =
(40.08) + 2(35.45) + 6(16.00) = 206.98 g/mol
50.0g Ca(ClO3)2 x 1 mole = 0.242 mole Ca(ClO3)2
206.98g
Sig Figs
Determine the mass of the following amount:
6.94 mol barium chloride (BaCl2)
Molar Mass BaCl2 = 137.33 + 2(35.45) = 208.23 g/mol
6.94 mol BaCl2 x 208.23 g = 1.45 x 103 g BaCl2
1 mole
Remember only 3 sig figs
Chemistry 20
Mole Conversions
Mole Conversions
Avogadro’s
Number
Respective
Particles
Moles
6.02 x 1023
molecules or
atoms or formula
units
Mole Conversion Examples
If a chemist is experimenting with 5 700 000 000
atoms of lead how many moles is she dealing
with?
Avogadro’s number = 6.02 x 1023 atoms
5 700 000 000 atoms Pb x 1 mole
= 9.5 x 10-15
mol
2 sig figs
6.02 x 1023 atoms
2 sig figs
How many moles is in 2.97 x 1025 atoms of
Vanadium?
2.97 x 1025 atoms of V x
1 mole
6.02 x 1023 atoms
= 49.3 moles of V
Determine the number of molecules in the
following:
a) 1.01 moles of bismuth
6.02 x 1023 atoms
1 mole
= 6.08 x 1023 atoms of Bi
1.01 mol Bi x
b) 2.5 moles of manganese
2.5 mol Mn x 6.02 x 1023 atoms
1 mole
= 1.5 x 1024 atoms of Mn
If the students in a chemistry 20 class have
7.66 x 1019 molecules of hydrogen peroxide,
H2O2, how many moles do they have?
7.66 x 1019 molecules x
1 mole
6.02 x 1023
molecules
= 1.27 x 10-4 molecules of H2O2
Chemistry 20
Mole Conversions
Mole Conversions
Litres of Gas at
STP
Volume
Moles
22.4 L
Mole Conversion Examples
Determine the volume, in liters, occupied by 0.030
moles of helium gas at STP.
0.030 moles He(g) x
22.4L
1 mole
= 0.67 L of He(g)
REMEMBER
UNITS
What is the volume of 0.05 mol of neon gas at
STP?
0.05 mol Ne x 22.4L = 1.12L of Ne(g)
1 mole
How many moles of argon atoms are present in
11.2 L of argon gas at STP?
11.2L Ar(g) x 1 mole = 0.5 mole Ar(g)
22.4L
What is the volume of 1.2 moles of water vapor
at STP?
1.2 mol H2O(g) x 22.4L = 26.88L of H2O
1 mole
Chemistry 20
Mole Conversions
Mole Conversions
Representative
Particles
x 6.02 x 1023
particles
1 mole
x 1 mole
6.02 x 1023 particles
MOLE
x 1mole
molar mass
X 22.4L
1 mole
Volume
at STP
x 1 mole
22.4L
x molar mass
1mole
Mass
Mixed Mole Conversion
1. Write down the question’s the given
and the unknown.
2. Convert the given unit to number of
moles.
3. Convert the number of moles found to
the unknown unit.
4. Make sure the answer has the correct
unit and number of sig figs.
Mole Conversion Examples
Calculate the mass, in grams (g), of the
following:
a) 3.00L of O2(g)
3.00L of O2(g) x 1 mole x 32.00 g = 4.29 g O2(g)
22.4L
1mole
b) 15 atoms of gold
15 atoms Au(s) x 1 mole x 196.97g = 4.9 x 10-21 g Au
6.02 x 1023 atoms 1 mole
Calculate the number of atoms in 2.0L of SO3
gas.
2.0L SO3(g) x 1 mole x 6.02 x 1023 atoms = 5.3 x 1022 atoms SO3
22.4 L
1 mole
If the students in a Chemistry 20 class have
3.25 x 105 molecules of CO2(g), how many litres
do they have?
3.25 x 105molecules of CO2(g) x 1 mole = 5.40 x 10-29 mole
6.02 x 1023 molecules
5.40 x 10-29 mole CO2 x 22.4L = 1.21 x 10-17 L CO2
1 mole

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