In This Lesson:
Unit 4
Moles and Mole
Conversions
(Lesson 1 of 4)
Stuff You Need:
Calculator
Periodic Table
Today is Friday (!),
October 30th, 2015
Happy Halloween sorta!
Pre-Class:
Take a look at the graduated
cylinder near the projector.
There are 18 mL of water in it.
If you had to guess, about how
many water molecules are in
there?
Also: You need your periodic
table and calculator.
Today’s Agenda
• The Mole!
• Working with Moles
• Where is this in my book?
– P. 287 and following…
By the end of this lesson…
• You should be able to calculate the number of
moles in a quantity of a substance.
The Mole
• 1 dozen of something equals how many?
– 12
• 1 mole of something equals how many?
– 6.02 x 1023 (or
602,000,000,000,000,000,000,000)
• For chemistry, a mole of a substance
equals 6.02 x 1023 representative particles.
– 1 mole of iron = 6.02 x 1023 iron atoms.
– 1 mole of carbon dioxide = 6.02 x 1023 carbon
dioxide molecules.
– 1 mole of sodium chloride = 6.02 x 1023 sodium
chloride formula units.
Did you get that?
• The smallest unit of a(n) ____ is a(n) ____:
– element…atom
– covalent compound…molecule
– ionic compound…formula unit
Avogadro’s Number
• 6.02 x 1023 is called
“Avogadro’s Number” in
honor of the Italian chemist
Amadeo Avogadro (17761855).
• He did not actually discover
the number, however.
• Fun fact: Avogadro’s full
name was Lorenzo Romano
Amadeo Carlo Avogadro,
Count of Quarequa and
Cerreto.
Amadeo Avogadro
Avogadro’s Number
Moles
Quick Mole Questions
• 1 Dozen Cars
• 1 Dozen Tricycles
– Of which vehicle do I have more?
• I have the same amount of each vehicle.
• 1 Mole of Molecule A = C2H6
• 1 Mole of Molecule B = C8H8
– Of which molecule do I have more?
• I have the same amount of each molecule!
Quick Mole Questions
• 1 Dozen Cars
• 1 Dozen Tricycles
– Do I have more car wheels or tricycle wheels?
• More car wheels (each car has 4, each tricycle has 3).
• 1 Mole of Molecule A = C2H6
• 1 Mole of Molecule B = C8H8
– Do I have more atoms from Molecule A or
Molecule B?
• More atoms from Molecule B (each B molecule has 16
atoms, each A molecule has 8 atoms).
How big is a mole?
• Video!
Molar Mass
• Molar mass (also known as formula mass) is the
total atomic mass of a compound or element.
– In other words, just add all the atomic masses of the
elements in a compound together.
• Molar mass equals the mass in grams of one mole of
a substance.
– One mole of hydrogen (H) has a mass of ~1.0079 g.
– One mole of hydrogen gas (H2) has a mass of ~2.016 g.
• Molar mass is measured in grams per mole or
g/mol.
Moles and Gases
• For solids, liquids, and gases, the molar mass
of a substance equals one mole.
• Also for gases, 22.4 Liters (L) = 1 mole.
– This works for any gas at STP (standard
temperature and pressure).
• This is called the molar volume.
– Like the molar mass, only…you know…volume.
So…
1 Mole
How much room (L)
So…
1 Mole
22.4 Liters (Gas)
Molar Mass Practice
• Calculate the molar mass of carbon dioxide.
• Formula of carbon dioxide = CO2.
• Carbon mass = 12.0107 g/mol.
• Oxygen mass = 15.9994 g/mol.
• 12.0107 + 15.9994 * 2 = 44.0095 g/mol.
• So, one mole of CO2, or 6.02 x 1023 molecules,
has a mass of about 44 grams.
Hydrates
• While we’re on the topic of formula mass, we
should talk about hydrates.
• Hydrates are substances, typically salts, that
contain water within their chemical bonds.
• Because of this, their formulas include H2O.
– Example: CoCl2 • 6H2O
– This is cobalt (II) chloride with six attached water
molecules.
Naming Hydrates
• CoCl2 • 6H2O is “Cobalt II chloride
hexahydrate.”
• CoCl2 • 5H2O is “Cobalt II chloride
pentahydrate.”
– I think you get the idea.
• CoCl2 is “Cobalt II chloride anhydrous,” which
just means it is not hydrated.
Hydrates
Hydrate Molar Mass
• We’ll look more at hydrates when we do our
Formula of a Hydrate lab. For now, know this:
– To calculate molar mass of a hydrate, add the mass of
water (times the coefficient) to the rest of the
formula’s mass.
– Example: CoCl2 • 6H2O
• Add up Co’s mass, Cl’s mass (times two) and water’s mass
(times six).
• 58.93 + 35.45 * 2 + 18.0148 * 6 = 237.9188 g/mol.
– The • looks like a multiplication symbol, but don’t do
that. That’d be bad.
Molar Mass Worksheet
• Let’s try a QUICK worksheet (Molar Mass) that
will help you practice molar/formula mass.
– Try 1/4 the problems. Any 10, as long as you do 10.
– You must try at least one of 30, 39, or 40, and at least
one of your ten has to have parentheses.
• ( ) around something means the subscript outside
them is distributive – you’ll need to do a little
multiplication for those.
– Example: Al2(SO4)3 – calculate SO4’s molar mass and
multiply by 3.
– Similar to what is done for hydrates.
Mole Calculations
• Now that you know how to find the mass of a
mole of something, it’s time to learn how to do
some calculations relating to that.
• The good news is we’re still going to be using our
old friend from unit analysis:
starting measurement target unit
given unit
• The other good news is that I have a system for
you to learn how to make these calculations.
– It’s called the mole highway.
The Mole Highway
Molar Mass 1 mol
x
x
1 mol
Molar Mass
Mass (g)
x
22.4 L
1 mol
x
1 mol
22.4 L
Volume (L)
x
6.02x1023
Rep. Part.
1 mol
1 mol
x
6.02x1023
Rep. Part.
Atoms, Molecules,
or Formula Units
The Mole Highway
x Molar Mass ÷ Molar Mass x 22.4 L
Mass (g)
÷ 22.4 L
Volume (L)
6.02x1023
x
Rep. Part.
6.02x1023
÷
Rep. Part.
Atoms, Molecules,
or Formula Units
Mole Conversion Triforce
L
mol
g
mol
molar
mass
22.4
rep.
part.
mol
6.02x
1023
Mole Calculations
• How many grams of lithium are in 3.50 moles of
lithium?
3.50 mol 6.941 g
=
1 mol
24.3 g
• There are 24.3 g of lithium in 3.50 mol.
Mole Calculations
• How many moles of lithium are in 18.2 grams of
lithium?
18.2 g
1 mol
= 2.61 mol
6.941 g
• There are 2.62 mol of lithium in 18.2 g.
Mole Calculations
• How many atoms of lithium are in 3.50 moles of
lithium?
3.50 mol 6.02 x 1023 atoms
= 2.11 x 1024 atoms
1 mol
• There are 2.11 x 1024 atoms of lithium in 3.50 mol.
The Big Idea
• As your Mole Highway shows:
– Moles  Grams = Multiply
• (MGM)
– Grams  Moles = Divide
Moles to Grams
2.55 moles of Cu2CrO4
619.868 grams
10.0 moles of NaCl
583 grams
3.00 moles of H2
6.05 grams
1.50 moles of potassium sulfate
261 grams
4.50 moles of sodium oxide
278 grams
1.95 moles of nitric acid
123 grams
2.20 moles of SnCl2
417 grams
3.27 moles of oxygen gas
105 grams
Grams to Moles
0.750 grams of Na2CO3
0.00708 moles
8.76 grams of NaOH
0.219 moles
25 grams of water
1.39 moles
88 grams of CO2
2 moles
25 grams of potassium permanganate
0.158 moles
17 grams of H2O2
0.5 moles
75.57 grams of potassium bromide
0.635 moles
100 grams of KClO4
0.722 moles
Let’s Talk About Gas
• You may have noticed another set of lanes on the
mole highway for volume.
• When it comes to gases, we can also determine
the volume a mole of a gas will take up (like we
can determine the mass of a mole of something).
• One mole of any gas takes up 22.4 L at standard
temperature and pressure.
– Molar mass doesn’t have anything to do with this.
• Conversions work the same way.
Mole Calculations
• How many liters do 2.00 moles of hydrogen gas
occupy at standard temperature and pressure?
2.00 mol 22.4 L
=
1 mol
44.8 L
• 2.00 moles of H2 take up 44.8 L.
Mole Calculations
• How many moles are in 14.2 liters of argon gas at
standard temperature and pressure?
14.2 L
1 mol
= 0.634 mol
22.4 L
• 14.2 L of Ar is 0.634 mol Ar.
The Big Idea
• As your Mole Highway shows:
– Moles  Liters = Multiply
– Liters  Moles = Divide
Moles to Liters
…and vice versa…
5.42 moles of Rn
121 liters
19.5 moles of F2
437 liters
13.21 moles of Ne
295.9 liters
2.37 moles of nitrogen gas
53.1 liters
11.9 liters of CO2
0.531 moles
1.3 liters of O3
0.058 moles
3.00 liters of CO
0.134 moles
90.2 liters of sulfur hexafluoride
4.03 moles
Mole Calculations
• How many atoms are in fifteen moles of lead?
15 mol
6.02 x 1023 atoms
= 9.0 x 1024 atoms
1 mol
• In 15 moles of Pb, there are 9.0 x 1024 atoms.
Mole Calculations
• How many moles are in 5.2 x 1024 molecules of F2?
5.2 x 1024 molecules
1
mol
6.02 x 1023molecules
= 8.6 moles
• If you have 5.2 x 1024 molecules of F2, you have 8.6
moles.
The Big Idea
• As your Mole Highway shows:
– Moles  Representative Particles = Multiply
– Representative Particles  Moles = Divide
Moles to Representative Particles
…and vice versa…
4.22 moles of Rn
2.54 x 1024 atoms
1.95 moles of F2
1.17 x 1024 molecules
1.23 moles of Ne
7.40 x 1023 atoms
23.7 moles of ammonium chloride
1.43 x 1025 formula units
5.32 x 1023 molecules of CO
0.884 moles
1.30 x 1025 molecules of O2
21.6 moles
3.00 x 1024 molecules of Cl2
4.98 moles
9.020 x 1024 atoms of cobalt
14.98 moles
Practice
• Mole Conversions Worksheet
– #1-6 [4 is a challenge]
• Mole Conversion Table Worksheet
– Get as far as you can…
Two Step Mole Conversions
• Sometimes you’ll need to go from grams to
liters or atoms to grams.
• In these cases, you’ll still use the mole
highway, but you’ll have to use it for two
steps.
• For example, let’s look at the path you’d take if
you needed to go from grams to atoms.
The Mole Highway
Molar Mass 1 mol
x
x
1 mol
Molar Mass
Mass (g)
x
22.4 L
1 mol
x
1 mol
22.4 L
Volume (L)
x
6.02x1023
Rep. Part.
1 mol
1 mol
x
6.02x1023
Rep. Part.
Atoms, Molecules,
or Formula Units
Mole Calculations
• How many atoms of lithium are in 18.2 grams
of lithium?
18.2 g
1
mol 6.02 x 1023 atoms
6.941 g
1
24
1.58
x
10
=
mol
atoms
• There are 1.58 x 1024 atoms of lithium in 18.2 g.
Mole Calculations
• How many formula units of sodium chloride
are in 14.0 grams of sodium chloride?
14.0 g
1
mol 6.02 x 1023 funits
58.44 g
1
23
1.44
x
10
=
mol formula units
• There are 1.44 x 1023 units of NaCl in 14.0 g.
Mole Calculations
• How many grams of water are in 1.204 x 1024
molecules of water?
1.204 x 1024
molecules
1
mol 18.0148 g
6.02 x 1023 molecules 1
mol
= 36.03 g
• 1.204 x 1024 molecules of water weigh 36.03 g.
Moles/Grams to Liters
(and vice versa)
0.600 mol SO2
13.44 liters
16 mol N
358.4 liters
16 mol N2
358.4 liters
38.44 g SO2
13.44 liters
40 L CO2 (convert to moles)
1.79 moles
40 L CO2 (convert to grams)
78.59 grams
16 L CO (convert to moles)
0.71 moles
16 L CO (convert to grams)
20.07 grams
Practice
• Mole Conversions worksheet
– #7-12
Closure
• Quick interesting note:
– For some reason, it seems like every two-step
mole conversion requires you to first divide, then
multiply.
• Multiply or divide by what? You decide.
– Example: Grams to Liters:
• Divide by molar mass, multiply by 22.4.
Closure
• How many representative particles are in
71.91 grams of diatomic bromine?
• Br2 formula mass = 159.81 g/mol
• 71.91 g / 159.81 g/mol = 0.45 moles
• 0.45 moles x 6.02 x 1023 = 2.709 x 1023
particles.
Mole Conversions Boss
• What mass of gold contains twice as many
atoms as 2.74 grams of silver?
• Au molar mass = 196.97 g/mol
=
• Ag molar mass = 107.87 g/mol
10.0 g Au
2.74 g Ag
1 mol Ag
2 mol Au 196.97 g Au
107.87 g Ag 1 mol Ag
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1 mol Au
Mole Conversions Boss 2
• Automobiles in the US emit approximately 1.5
billion metric tons of carbon dioxide annually.
How many liters is this at STP?
=
• 1 metric ton = 2204.6 pounds
14 L
7.7
x
10
• 2.2 pounds = 1 kilogram
1.5x109 t 2204.6 lbs 1 kg 1000 g 1 mol 22.4 L
1t
2.2 lbs 1 kg 44.009 g 1 mol
https://www.fueleconomy.gov/feg/climate.shtml
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