Download The Mole

CHEMISTRY WARM UP (BACK TO
CONVERSIONS!!!!)



Convert the following:
5.5 dozen apples = _____ kg apples (1 dozen = 2.0
kg apples)
3 dozen apples = _____ bushel apples (1 dozen
apples = .20 bushel apples)
SECTION 1
THE MOLE: A MEASUREMENT OF MATTER
Key Concepts




What are three methods
for measuring the
amount of something?
How is avogadro’s
number related to a
mole of any substance?
How is the atomic mass
of an element related to
the molar mass of an
element?
How is the mass of a
mole of a compound
calculated?
Vocabulary
Mole
 Avogadro’s Number
 Representative
Particle
 Molar Mass

HOW DO WE MEASURE THINGS WE CAN’T
SEE LIKE THE ATOM?
The Mole – the animal
The Mole – chemistry 
MEASURING MATTER

Measure the amount of something by:
Count (how many)
 Mass (g)
 Volume (mL or cm3)

MATTER

Composed of:
Atoms
 Molecules
 Ions

Counting them would take forever!
THE MOLE
-A UNIT THAT IS A SPECIFIC NUMBER OF
PARTICLES

One Mole
6.02 x 1023 “representative particles”
 Avogadro’s Number



Atoms


1 mole of Aluminum = 6.02 x 1023 atoms
Molecules


“Representative Particles”
1 mole of H20 = 6.02 x 1023 molecules
Formula Units (a.k.a. ionic compounds)

1 mole of CaF2 = 6.02 x 1023 formula units
AMEDEO AVOGADRO DI QUAREGNA
Italian scientist
 Helped clarify the
difference between
atoms and molecules

CONVERTING NUMBER OF REP. PARTICLES
TO MOLES
Generic conversion:
1 mole = 6.02 x 1023 “representative particles”
Examples:
 How many atoms in one mole of Copper?


How many formula units in 2 moles of NaCl?
PRACTICE

How many atoms are on three moles of Calcium?

How many molecules are in 2.5 moles of Al2Cl6?

How many formula units are in 10 moles of
NaCl?
PRACTICE WORKSHEET
WARM UP

How many moles is 2.80 x 1024 atoms of Silicon?

How many formula units in 2 moles of MgBr2?
CONVERTING MOLES TO NUMBER OF
ATOMS (IN A COMPOUND)

First, figure out the number of atoms in the
compound.
 Example: H20


1 mole of H20 contains 6.02x1023 molecules


3 atoms per molecule
BUT each molecule of water contains 3 atoms
Moles  Molecules  Atoms
CLASS EXAMPLE:

Propane is a gas used for cooking and heating.
How many atoms are in 2.12 mol of propane?
(C3H8)
PRACTICE:

How many atoms are in 1.14 mol of SO3?

How many moles are in 4.65x1024 atoms NO2?
THE MASS OF A MOLE OF AN
ELEMENT
MOLAR MASS
Numbers under the elements on the periodic
table
 The mass of ONE mole of a substance
 Example:

Molar mass of Carbon = 12.0 grams
 1 mole of Carbon = 12.0 grams

Molar Mass of Oxygen = 16.0 grams
 1 mole of Oxygen = 16.0 grams

EXAMPLE

How many moles is 2 grams of Lithium?

How many grams is 5 moles of Tin?
ONE MOLE OF VARIOUS ELEMENTS
MOLAR MASS CONTINUED…JUST THINK!
1 mole of hydrogen has 6.02x1023 atoms and
weighs 1.008 grams…
 1 mole of carbon has 6.02x1023 atoms and weighs
12 grams…
 How can they have the same number of
atoms but weigh different amounts?

THE MASS OF A MOLE OF A
COMPOUND
MOLAR MASS OF A COMPOUND
To calculate the molar mass of a compound:
 Separate out EACH element
 Count the number of that element
 Multiply by the molar mass
 Add the masses of the elements in the compound


Example: SO3
Element
S
O
Number of
Molar
Mass
Total Mass
EXAMPLE

H 2O

CH4

C6H12O6
SECTION 1 ASSESSMENT - JIGSAW
1. What are three ways to measure the amount of
something?
 2. Describe the relationship between Avogadro’s
number and one mole of any substance.
 3. How is the atomic mass of an element related
to the molar mass of the element?
 4. How can you calculate the mass of a mole of a
compound?
 5. How many moles is 1.50 x 1023 molecules of
NH3?
 6. How many atoms are in 1.75 mol CHCl3?
 7. What is the molar mass of CaSO4?
 8. How many moles are in 4.65 x 1024 molecules
of NO2?

SECTION 2
Key Concepts
Convert the mass of a
substance to the
number of moles
 What is the volume of
a gas at STP

Vocabulary
Avogadro’s hypothesis
 Standard
Temperature and
Pressure (STP)
 Molar Volume

THE MOLE-MASS RELATIONSHIP
Use the molar mass of an element or compound
to convert between the mass of a substance and
the mass of a substance.
 Conversion factor: molar mass = 1 mole

Equations:
 Mass(grams) = number of moles x mass(grams)
1 mole

Moles = number of grams x ___1 mole____
mass(grams)
Molar Mass
CLASS EXAMPLES:

Aluminum satellite dishes are resistant to
corrosion because the aluminum reacts with
oxygen in the air to form a coating of aluminum
oxide (Al2O3). This tough, resistant coating
prevents any further corrosion. What is the mass
of 9.45 mol of aluminum oxide?
CLASS EXAMPLE

When iron is exposed to air, it corrodes to form
red-brown rust. Rust is iron(iii)oxide (Fe2O3).
How many moles of iron oxide are contained in
92.2 g of pure iron oxide?
PRACTICE


Find the mass in grams of 4.52 x 10-3 mole
C20H42.
Calculate the mass, in grams, of 2.50 mole of
iron(ii)hydroxide.
PRACTICE


Find the number of moles in 3.70 x 10-1 g of
boron.
Calculate the number of moles in 75.0 g of
dinitrogen trioxide.
PRACTICE WORKSHEET
PRACTICE: FIND THE MASS, IN GRAMS, OF 1.00
X 1023 MOLECULES OF N2.
PRACTICE: FIND THE MASS IN GRAMS OF 2.00 X
1023 MOLECULES OF F2
PRACTICE: HOW MANY ATOMS OF NITROGEN
ARE IN 1.2 GRAMS OF ASPARTAME? C14H18N2O5
PRACTICE: FIND THE MASS IN 2.6 X 1043
MOLECULES OF LITHIUM BROMIDE.
THE MOLE-VOLUME RELATIONSHIP
AVOGADRO’S HYPOTHESIS

The equal volumes of gases at the same
temperature and pressure contain equal numbers
of particles
Despite differences in the size of the atoms
 Due to the fact that the gas particles are so far apart

S.T.P.

Gases are measured at Standard Temperature
and Pressure


B/C of variations that result in volume
STP
Temperature: 0 degrees Celcius (273 K)
 Pressure: 101.3 kPa or 1 atm

MOLAR VOLUME
At STP:
 1 mol or 6.02 x 1023 representative particles of
any gas occupies a volume of 22.4 L.

CALCULATING VOLUME AT STP


Convert MOLES of gas to the VOLUME of gas
at STP
Conversion factor: 22.4 L = 1 mol
CLASS EXAMPLE:

Sulfur dioxide is a gas produced by burning coal.
It is an air pollutant and one of the causes of acid
rain. Determine the volume, in liters, of 0.60 mol
sulfur dioxide at STP.
EXAMPLES
What is the volume of these gases at STP?
 3.20 x 10-3 mol CO2


3.70 mol N2
EXAMPLES
At STP, how many moles does each of the
following gases occupy?
 1.25 L He


0.335 L C2H6
PRACTICE


What is the volume, in Liters, of 15 g of H2 at
STP?
What is the volume, in Liters, of 3.4 x 1028
molecules of O2 at STP?
PRACTICE WORKSHEET
CALCULATING MOLAR MASS FROM
DENSITY

Density:

Measured in grams per liter (g/L)
General Equation
 Molar Mass = density at STP x molar volume at
STP


Grams = grams x 22.4L
Mole
L
Mole
CLASS EXAMPLE

The density of a gaseous compound containing
carbon and oxygen is found to be 1.964 g/L at
STP. What is the molar mass of the compound?
EXAMPLES

A gaseous compound composed of sulfur and
oxygen, which is linked to the formation of acid
rain, has a density of 3.58 g/L at STP. What is
the molar mass of this gas?
EXAMPLES

What is the density of krypton at STP?
SECTION ASSESSMENT (10.2)