Molar mass - skylinecpchemistry

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1 mole =
6.02 X
23
10
things
This is called Avogadro’s number
Molar mass
Molar mass is the mass of a mole of that thing
The molar mass of pennies is the mass of
6.02X1023 pennies (about 2X1024 grams)
2 million million million tons of pennies
The molar mass of carbon is the mass of
6.02X1023 carbon atoms (which happens to be
exactly 12 grams)
Molar mass
The molar mass of:
Ca = 40.08 grams
MgCl2 = 95.2 grams
H2O = 18 grams
(using the periodic table)
Moles
There are one mole of:
Atoms in 40.08 grams of Ca (element)
Formula units in 95.2 grams of MgCl2 (ionic)
Molecules in 18 grams of H2O (molecular)
Remember that representative particles refer
to the types of substances we are measuring
Moles
1 mole of atoms in 40.08 grams of Ca
3 moles of atoms in 95.2 grams of MgCl2
3 moles of atoms in 18 grams of H2O
This will come in handy when we study
chemical reactions.
Moles
Gram atomic mass (GAM) refers to the mass of
one mole of atoms of an element
Gram molecular mass (GMM) refers to the mass of
one mole of molecules of a compound
Gram formula mass (GFM) refers to the mass of
one mole of formula units of an ionic compound
6.02 X 1023 remember this number
Name
Formula
Representative
particle
Strontium
Sr
atom
Iron
Cobalt
Silicon
Aluminum
Element 1 Element 2 Element 3
Sr
-
-
Gram
atomic
mass
(GAM)
87.6 g
Name
Magnesium
sulfate
Potassium
iodide
Calcium
sulfite
Lithium
oxide
Beryllium
fluoride
Representative
Formula
Element 1 Element 2
particle
MgSO4
Formula unit
Mg
S
Element 3
Gram formula
mass
(GFM)
4O
123.3 g
Name
Formula
Carbon
tetrachloride
CCl4
Carbon
monoxide
Silicon
dioxide
Nitrogen
Dihydrogen
sulfide
Representative
Element 1 Element 2
particle
molecule
C
Cl
Element 3
Gram
molecular
mass
(GMM)
-
153.8 g
How many moles in 26.8 grams of iron?
How many moles in 26.8 grams of iron?
We are given grams of iron, so that goes
on the left
We want moles, so that must end up on
the right
Make conversion factors do that
How many moles in 26.8 grams of iron?
26.8 g Fe
given
mole Fe
55.85 g Fe
Conversion
factor
How many moles in 26.8 grams of iron?
26.8 g Fe
mole Fe
55.85 g Fe
Cancel units in numerator and denominator
How many moles in 26.8 grams of iron?
26.8 g Fe
mole Fe
55.85 g Fe
.48 mole Fe
We will need to be able to figure out
how many grams are in a certain
number of moles.
We use the same conversion factor
as we just did, only inverted.
How many grams in .48 moles of iron?
How many grams in .48 moles of iron?
.48 mol Fe
given
55.85 g Fe
mol Fe
Conversion
factor
How many grams in .48 moles of iron?
.48 mol Fe
55.85 g Fe
Mol Fe
Cancel units in numerator and denominator
How many grams in .48 moles of iron?
.48 mol Fe
55.85 g Fe
mol Fe
26.8 g Fe
Conversion factors:
12 in / 1 ft
1 ft / 12 in
5280 ft / 1 mi
1 mi = 1.61 km
1 mi / 5280 ft
1.61 km / 1 mi
Conversion factors for calculating
moles and grams:
12 g C / mol C
Mol C / 12 g C
153.8 g CCl4 / mol CCl4
Mol CCl4 / 153.8 g CCl4
123.3 g MgSO4 / mol MgSO4
Mol MgSO4 / 123.3 g MgSO4
Things we’ll need to be able to do:
• Write chemical formulas from chemical names
– Magnesium sulfate is MgSO4
• Calculate molar mass from chemical formulas
– 123.3 g MgSO4 is one mole MgSO4
• Use conversion factors to calculate moles
from mass, and mass from moles
– 123.3 g MgSO4 / mol MgSO4
– mol MgSO4 / 123.3 g MgSO4
How many grams in .06 mole
potassium nitrate?
How many grams in .06 mole
potassium nitrate?
• Formula?
How many grams in .06 mole
potassium nitrate?
• Formula?
• Molar mass?
How many grams in .06 mole
potassium nitrate?
• Formula?
• Molar mass?
• Conversion factor?
How many grams in .06 mole
potassium nitrate?
.06 mol KNO3
given
101 g KNO3
mol KNO3
conversion
factor
6.06 g KNO3
How many moles in 486 grams
aluminum sulfate?
How many moles in 486 grams
aluminum sulfite?
• Formula?
How many moles in 486 grams
aluminum sulfite?
• Formula?
• Molar mass?
How many moles in 486 grams
aluminum sulfite?
• Formula?
• Molar mass?
• Conversion factor?
How many moles in 486 grams
aluminum sulfite?
486 g Al2(SO3)3
given
mol Al2(SO3)3
294 g Al2(SO3)3
conversion
factor
1.65 mol Al2(SO3)3
1 mole of any
element
6.02 X 1023
atoms of that
element
1 molar mass
of that
element
How many molecules in 287 grams
carbon dioxide?
How many molecules in 287 grams
carbon dioxide?
• Formula?
How many molecules in 287 grams
carbon dioxide?
• Formula?
• Molar mass?
How many molecules in 287 grams
carbon dioxide?
• Formula?
• Molar mass?
• Conversion factor?
How many molecules in 287 grams
carbon dioxide?
287 g CO2
given
6.02 X 1023 molecules CO2
44 g CO2
conversion
factor
3.93 X1024
molecules CO2
1. How many grams are in 2.73 moles of
sodium chloride?
2. How many moles are in 682 grams of
strontium nitrate?
3. How many representative particles are
in .187 grams of copper(II) sulfate?
4. How many atoms are in 87.1 grams of
magnesium chloride?
5. 239 grams of carbon tetrachloride is
how many moles of molecules?

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