MOLAR MASS
What is molar mass?
How do you calculate molar mass?
WHAT IS MOLAR MASS?
• mass in grams of 1 mole of the element
• Molar Mass
(MM)
=
___grams____
1 Mol
Synonyms: molecular weight, gram formula unit
Use Periodic Table to determine MM!
• Let’s examine periodic table!
• If I had one mole of _____ it’s molar mass would
be _______ g per 1 mol.
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Carbon
Atomic Hydrogen
Mercury
Iron
Sulfur
MM= 12.0 g / mol
MM= 1.0 g / mol
MM= 200.6 g / mol
MM=55.8 g / mol
MM= 32.1 g / mol
How many particles do
these elements contain?
Particles:
1. Atoms
2. Formula Units
3. Molecules
How do you calculate
molar mass of compounds?
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SO
3
EX. Sulfur Trioxide Chemical Formula = _____________
How many total atoms make up one molecule?
1+3=4
Atoms = _____________
1 x ______
32.1 = 32.1
S: ___
48.0 +
16.0 = _____
3 x ______
O: ___
80.1
80.1 grams per
• The molar mass of sulfur trioxide = _______
1 mol
________
Your Turn
PCl3
• EX. Phosphorus Trichloride
Chemical Formula = __________
1+3=4
• How many total atoms make up one molecule? Atoms = ________
1 x ______
31.0
31.0 =
• P: ___
3 x ______
35.5 = _________
106.5 +
• Cl: ___
137.5 grams per 1 mol
• Sodium Hydrogen Carbonate
NaHCO3
MM = 84.0 g / mol
Representative Particles
molecules
• Covalent Compounds are made up of _____.
Formula units
• Ionic Compounds are made up of _________.
atoms
• Elements are made up of _____________.
• Use your Road Map!
Conversions Using Molar Mass
• Book pg. 298
Al2O3
• Ex. #1 Write the chemical formula for aluminum oxide _________
• What is given? 9.45 moles
Trying to find? g of Al2O3
moles Al2O3 x _______________
102.9 grams Al2O3 =
• 9.45
______________
GIVEN
1 Mole Al2O3
Al: 2 x 27.0 = 54.0 g
O: 3 x 16.0 = 48.0 g +
102.0 g / 1 mol
964 g of Al2O3
Molar Volume Conversions
• At STP (Standard Temp and Pressure):
• 1 mole of gas = 22.4 L = 6.02 x 1023 particles
1 Mole of ANY GAS at STP!
• Sample Problem 10.7
• Sample Problem 10.8
Use our Mole Road Map!
• REMEMBER! Density = mass =
grams
Volume
Liter
• HINT: If given density, first find the molar mass
(MM) = grams per mol