Unit 5 – Chemical Quantities & The Mole
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Unit 5 – Chemical Quantities & The
Mole
Molar mass is the mass of one moleof a substance.
Other names for molar mass include…*formula mass
*gram formula mass*molecular weight
Molar Mass
Molar Mass
• One _____________of any element will
have a mass in grams corresponding to
the value of its ____________________.
o1 mol carbon = __________ g/mol
o1 mol calcium = ___________ g/mol
o(its atomic mass from the periodic table
= 1 mole)
mole
atomic mass
12.011
40.078
Diatomic Elements never exist alone in
nature!!!
*Trick for remembering the 7 diatomics *
Molar Mass of Compounds
• One ________ of any
molecule/compound will have a
mass in grams corresponding to the
value of its molar mass (the sum of the masses of the elements that
compose it).
mol
http://app.discoveryeducation.com/search?Ntt=moles
Example: Water, H2O
Element Molar Mass # of Atoms Total
H
O2
1
1.008
15.999
X
X
2.016 g
15.999 g
18.015 g/mol
This is the mass of 1 mol of water!
Ex. Ca(NO3)2
Ca: 40.078 x 1 = 40.078
N: 14.007 x 2 = 28.014
O: 15.999 x 6 = 95.994
--------------
164.086 g/mole
Sample Problems
Potassium carbonate ___________K2CO3
# of K atoms: x =+
# of C atoms: x =+
# of O atoms: x =
___________________
39.098
12.011
15.999
2
1
3
78.196
12.011
47.997
138.204 g K2CO3
Sample Problems
Ammonium sulfate _____________(NH4)2SO4
# of N atoms: x =+
# of H atoms: x =+
# of S atoms: x =+
# of O atoms: x =
_________________________
14.007
1.008
32.066
2
8
1
28.014
8.064
32.066
132.140 g (NH4)2SO4
15.999 4 63.996
Practice
1. What is the atomic mass of sodium?
2. Calculate the molar mass of Al2(SO4)3
3. Calculate the molar mass of nitrogen
(hint: diatomic!?!?).
Mole HighwayNOTES: To convert between units, follow the highway. Notice, there is no shortcut from grams to liters or between any of the three units surrounding the mole.
This means you have to convert to molesbefore converting to another unit!
Draw the Mole Road Map!!
Molar mass:
• called gram atomic mass when single element is used.
• called gram formula unit when ionic compound is used.
• called gram molecular unit when molecular compound or
diatomic molecules used.
• Diatomic molecules are atoms that bond with themselves.
There are SEVEN of these that you need to remember: Br2 I2N2 Cl2 H2 O2 F2 (Remember this by the name “BRINClHOF”)
Determine the number of moles in….
• 25 g sodium
25 g 1 mol
22.990 g= 1.1 mol
Molar mass of Sodium =
Na = 1 x 22.990 = 22.990 g
Determine the number of moles in….
• 85 g H2SO4
85 g 1 mol
98.078 g= 0.87 mol
Mass in grams of H2SO4 =
H = 2 x 1.008 =
S = 1 x 32.066 =
O = 4 x 15.999 =
Add to get molar mass of 98.078 g
Determine the number of grams in….
• 2.5 moles of sodium
2.5 mol 22.990 g
I mol= 57 g
Molar mass of Sodium =
Na = 1 x 22.990 = 22.990 g
Determine the number of grams in….
• 0.50 moles of H2SO4
0.50 mol 98.078 g
I mol= 49 g
Mass in grams of H2SO4 =
H = 2 x 1.008 =
S = 1 x 32.066 =
O = 4 x 15.999 =
Add to get molar mass of 98.078 g
How many moles are there in 27 g of
ethanol (C2H5OH)?
27 g 1 mol
46.069 g= 0.59 mol
Mass of C2H5OH:
C = 2 x 12.011=
H = 6 x 1.008=
O = 1 x 15.999=
Add these all up for mass in grams = 46.069 g
Homework page 7
Show all work and units to receive full credit.
Representative Particles Moles
It’s a quantity, and it’s a BIG one.
• Avogadro’s Number = ______________
and is also called a _______.
• Like a “pair” or “dozen,” a “mole”
represents a set number of things; in
chemistry, those “things” are particles.
For example:
• 1 dozen = ______ items
• 3 dozen = ______ cookies
• .5 dozen = ______ doughnuts
6.02 x 1023
Mole
12
36
6
It’s a quantity, and it’s a BIG one.
So, a “dozen” is a counting unit
equal to __12__of any object.
Likewise, a “Mole” is a counting
unit equal to _____________ of an
object, even really small ones like
____________, ____________, or
_____________.
6.02 x 1023
atoms molecules
formula units
What’s so special about 6.02 x 1023?
• Why do scientists use that number?
oA conversion factor.
oAllows us to manipulate many small
particles, as if they were one whole
part.
o For elements on the periodic table, there is a 1
to 1 relationship between the mass of a single
atom (in amu) and the mass of 1 Mole of the
same species of atom (in grams).
o Remember, Mole is a quantity…6.02 x 1023
particles.
What’s so special about 6.02 x 1023?
Using the periodic table, we’ve learned that an Argon atom has a mass of 39.95 amu.
Unfortunately, manipulating a single atom of any element isn’t reasonable, so taking its individual mass isn’t possible.
However, we do have the Mole…
Atomic Number
(number of protons)
Atomic Mass
(average number of
protons and neutrons)
Ar
1 Atom of Argon 1 Mole of Argon
•So, a 39.95 g sample of
Argon contains 6.02 x 1023
atoms…that’s Avogadro’s
Number, the MOLE!
•It’s a 1 to 1 relationship
between a single atom in
amu and a Mole of atoms
in grams.
Representative Particles
• A representative particle
is the smallest unit of a
substance.
Types of Particles
• Monatomic elements = _______________
• Diatomic elements = _________________
• Ionic compounds = _________________
• Covalent compounds = ______________
• Ions = _________________
• Acids = _________________
atoms
molecules
formula units
molecules
atoms
molecules
Avogadro’s number, which is
________________, represents the
number of “chemical units” in
one mole of any substance. For
the monatomic elements, the
“chemical unit” is an __________.
1 mol of any chemical =
______________ particles.6.02 x 1023
atom
6.02 x 1023
Examples
• 1 mol CaCl2 =
• 1 mol Ca2+ =
• 1 mol HCl (aq) =
• 1 mol P2O5 =
• 1 mol Ca =
• 1 mol Cl2 =
6.02 x 1023 formula units
6.02 x 1023 atoms
6.02 x 1023 molecules
6.02 x 1023 molecules
6.02 x 1023 molecules
6.02 x 1023 atoms
1. How many moles are in 4.50 x 105
atoms of manganese?
4.50 1025 atoms 1 mol
6.02 1023 atoms
= 74.8 moles
Sample problems
2. How many atoms are found in
3.27 mol of magnesium?
3.27 mol 6.02 1023 atoms
1 mol
= 1.97 1024 atoms
Sample problems
3. Chalk is composed primarily of calcium
carbonate. How many particles are in
3.4 moles of calcium carbonate?
3.4 mol 6.02 1023 formula units
1 mol
= 2.0 1024 formula units
Sample problems
Moles of Chalk Lab
Homework page 10
Show all work and units to receive full credit.
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