What
is a
MOLE?
There are 12
items in a dozen
There are 144 items in a gross
of any substance
There are 6.02 x 1023 atoms or
molecules in a mole of any substance
I’m going to need
a bigger shovel!
23
10
6.02 x
=
602, 000,000,000,000,000,000,000
A mole of standard soft drink cans
would cover the surface of the Earth to
a depth of over 200 miles.
If you had a mole of unpopped popcorn kernels, and
spread them across the United States of America,
the country would be covered in popcorn to a
depth of over 9 miles.
Molar mass is the weight of one
23
mole (or 6.02 x 10 molecules)
of any chemical compounds.
Molar Masses
Water’s molar mass is
18 grams
PVC’s molar mass is
150,000 grams
How can I find the molar mass
of an element?
Use the element’s
mass on the periodic table
Example: What is the molar mass
of Carbon?
Carbon’s atomic mass is……12.01
Therefore, Carbon’s molar mass is…..
12.01g
Example: What is the molar mass
of Magnesium?
Magnesium’s atomic mass is……24.31
Therefore, Magnesium’s molar mass is…..
24.31g
Example: What is the molar mass
of Krypton?
Krypton’s atomic mass is……83.80
Therefore, Krypton’s molar mass is…..
83.80g
Practice Time!
Element
Molar Mass Element
Helium (He)
Argon (Ar)
Chlorine
(Cl)
Sodium (Na)
Neon (Ne)
Phosphorus
(P)
Molar mass
Now,
let’s
kick it
up a
notch!
To calculate the molar mass of a
compounds
• First you find the molar mass of the parts of
the compound and then you add.
• If there are more than one of a type of atom
in the compound, you multiply the number of
atoms time the molar mass of the one atom,
and then add all parts together.
What’s the molar
mass of a compound
like NaCl?
Molar mass of Na = 22.99
Molar mass of Cl = 35.45
22.99
+35.45
So, the Molar
mass of NaCl = 58.44g
What’s the molar mass of
C6H12O6?
Molar mass of C6= 6 x 12.01 = 72.06
Molar mass of H12=12 x 1.008 = 12.096
Molar mass of O6= 6 x 16.00= 96
So, the Molar mass
of C6H12O6 =
72.06
+12.096
+96
=180.156 g
Practice Time!
Compo Molar Mass
und
Carbon
dioxide
(CO2)
Compo Molar mass
und
Ammo
nia
(NH3)
Ethanol
(C2H6O
)
Sulfuri
c acid
(H2SO4
)
Calculate the Molar Mass:
Ca(NO3)2
Percent Composition
A percent is a ratio.
Sometimes we want to know how much of an
element is in the compound.
Steps to determine percent
composition
1. Calculate the molar mass from the formula.
2. Determine how many grams the atom of interest
contributes to the compound
3. Divide the mass of the atom by the molar mass
and multiply by 100 to get a percentage.
% Composition = Mass of the element in cmpd x 100
Molar Mass of cmpd
Example: Find the % of Na and Cl in
NaCl
Sodium Chloride, NaCl
Na = 22.99g
Cl = 35.45g
%Na = 22.99 x 100
58.44
%Cl = 35.45 x 100
58.44
Molar Mass = 58.44g
=39.34 % Na
= 60.7% Cl
Find the % of each element in Na2SO4
Give the % composition of all the
elements in
Magnesium sulfite
Formula
Relating Moles & Mass
What you already know….
How big is a mole?
6.02 x 1023 atoms or molecules
How do you determine molar It’s the same as atomic mass.
mass of an atom?
How do you determine molar
mass of a molecule?
It’s the same as the sum of the
atomic masses of the parts.
Chemist use moles to understand relationships
between reactants and products. In the lab
we don’t have a balance that measures moles.
We must relate grams to the number of moles.
What you don’t know
• How many moles are
in this glass of water?
What else you don’t know
• Can you add 3.25
moles of water to the
beaker?
These two questions
can be solved by
using
!
conveRsins
A Conversion is just a math equation in
which you
1. START with the data and units they
give you in the problem, and then
2. MULTIPLY by CONVERSION FACTORS
until you have the right units at the
end.
What’s a Conversion Factor?
It’s a FRACTION in which the TOP
number and BOTTOM number
mean the same thing but have
different
units.
12 eggs
3 feet
1 yard
1 dozen
1 week
7 days
100 yards
1 football field
1 cup
8 ounces
6 points
1 touchdown
Write 3 of your own!
Mole Conversion
Molar Mass
1 Mole
or
1 Mole
Molar Mass
How do you know which part to put
on top and which part to put on
bottom?
Because
12 eggs
1 dozen
Is the same thing as
1 dozen
12 eggs
How do you know which one to
use?
RULE!!!!
Use the conversion factor with the
UNITS of the info they give you in
the problem on the BOTTOM and
the UNITS of what you’re
LOOKING FOR on the TOP!!
So, if they tell you there are 8 dozen and
ask you how many eggs there are:
START with what they give you
8 dozen
By a conversion factor that
MULTIPLY connects eggs to dozens. How
many eggs in ONE dozen?
X
12 eggs
1 dozen
NOTE: The “dozen” in the first number and the “dozen” in the
bottom of the conversion factor will cancel each other out,
leaving eggs!!!
= 96 eggs
For example:
How many grams are in 3 moles of
Carbon?
START with what they give you
3 moles
By a conversion factor that
MULTIPLY connects moles to grams. How
many grams in ONE mole of
hydrogen?
X
12.00 grams
=36.00 g
1 mole C
NOTE: The moles in the first number and the moles in the
bottom of the conversion factor will cancel each other out,
leaving grams!!!
Another example, this time a little trickier:
How many grams are in 5 moles of
carbon dioxide (CO2)?
START with what they give you
By a conversion factor that
MULTIPLY connects moles to grams. How
many grams in ONE mole of
carbon dioxide?
5 moles CO2 X
44.01 grams = 220.05 g
1 mole CO2
NOTE: The moles in the first number and the moles in the
bottom of the conversion factor will cancel each other out,
leaving grams!!!
Steps to conversions
1.
2.
3.
4.
5.
Write the given.
Draw a “times and a line”
Write the units you were given on the bottom
Write the units you want on top
Fill in the conversion factor (remember 1 is
always with the mole)
6. Multiply all the numbers on the top and divide it
by the numbers on the bottom.
Practice Time!
•
How many grams are there in 350 moles of iron (Fe)?
•
How many grams are there in 3 moles of Lithium (Li)?
•
How many grams are there in 46 moles of water (H2O)?
•
How many grams are there in 12.7 moles of magnesium chloride (MgCl2)?
•
A chemist needs 12.5 moles of sulfuric acid (H2SO4). How many grams does he
need?
•
How many grams are there in 350 moles of iron (Fe)? 19547.5 g
•
How many grams are there in 3 moles of Lithium (Li)? 20.82 g
•
How many grams are there in 46 moles of water (H2O)? 828.92 g
•
How many grams are there in 12.7 moles of magnesium chloride (MgCl2)?
1209.04 g
•
A chemist needs 12.5 moles of sulfuric acid (H2SO4). How many grams does he
need? 1226 g
Those problems you just finished were all
“MOLES TO GRAMS ” problems because they
GAVE you moles and asked you to find grams.
We could, on the other hand, give you GRAMS
and ask you to find MOLES. That would be a
GRAMS TO MOLES problem.
For example:
How many moles are in 250 grams of
Carbon?
START with what they give you
By a conversion factor that
MULTIPLY connects moles to grams. How
many grams in ONE mole of
carbon?
250 grams X
1 mole C
12.00 grams
NOTE: The grams in the first number and the grams in the
bottom of the conversion factor will cancel each other out,
leaving moles!!!
= 20.83
moles
Another example, this time a little trickier:
How many moles are in 930 grams of
carbon dioxide (CO2)?
START with what they give you
By a conversion factor that
MULTIPLY connects moles to grams. How
many grams in ONE mole of
carbon dioxide?
930 grams X
1 mole CO2
44.01 grams
NOTE: The grams in the first number and the grams in the
bottom of the conversion factor will cancel each other out,
leaving moles!!!
= 21.13
moles
Practice Time!
•
How many moles are in 2.4 grams of sulfur (S)?
•
How many moles are in 18.7 grams of argon (Ar)?
•
How many moles are in 88.1 grams of potassium chloride (KCl)?
•
How many moles are in 2.3 grams of nitric acid (HNO3)?
•
How many moles are in 11.9 grams of calcium hydroxide - Ca(OH)2? (Don’t forget!
The 2 subscript applies to the O and to the H!!)
•
How many moles are in 2.4 grams of sulfur (S)? 0. 0748 mol S
•
How many moles are in 18.7 grams of argon (Ar)? 0.468 mol Ar
•
How many moles are in 88.1 grams of potassium chloride (KCl)? 1.18 mol
•
How many moles are in 2.3 grams of nitric acid (HNO3)? 0.036 mol
•
How many moles are in 11.9 grams of calcium hydroxide - Ca(OH)2? (Don’t forget!
The 2 subscript applies to the O and to the H!!) 0.16 mol
Stoichiometry
• The study of quantitative relationships
between reactants and products
• Balanced chemical equations relate moles of
reactants to moles of product
N2 + 3H2  2NH3
• The coefficients are the mole ratio
• 1 mole of N2 and 3 moles of H2 make 2 moles
of NH3
Sample Problems
2 KClO3  2KCl + 3O2
2 moles of KClO3 can produce __ moles of KCl.
4 moles of KClO3 can produce __ moles of KCl.
Theoretical Yield
• Yield = the amount of product
• Goal – make as much of the product as
possible
• Theoretical Yield – the most you should make
as predicted by the chemical reaction using
stoichiometry: N2 + 3H2  2NH3
Actual Yield
• the amount of product actually produced in
the lab
• Usually lower due to collection techniques
and apparatus used
• If the amount is higher than predicted then
there may be impurities in the product
Percent Yield
• Measures how well you did the lab
Percent yield = Actual yield
x 100
theoretical yield
Do Now
Balance the reaction
____ NaCl + ____ F2  ____ NaF + ____ Cl2
For every 2 moles of NaCl, ___ moles of NaF are produced.
For every 2 moles of NaCl, ___ moles of Cl2 are produced.
For every 4 moles of NaCl, ____ moles of NaF are produced.
• Work on assignment 8
• Try the practice quiz
• Do NOT copy
Limiting Reactant
• The reactant that is used up first
Making a bicycle requires
1 frame + 2 wheels  1 bicycle
If you have 10 frames and 12 wheels, how
many bicycles can you manufacture?
What is the limiting reactant?