Download Lesson 1 - St John Brebeuf

The Mole Concept
Lesson 1
Chemical Calculations
Atoms and molecules are EXTREMELY
small.
If they are so small and so light how are we
suppose to measure and weigh them?
Answer
We weigh large numbers of them to get
them into GRAMS/MOLE…. g/mol
Avogradro took did
experiments and
determined how many
Hydrogen atoms it would
take to weigh 1.00 grams.
He found that:
To get 1.00 grams of hydrogen you needed:
6.02 x 1023 hydrogen atoms.
He referred to this number as a mole.
Avogradro’s Number
Avogradro’s Number = 6.02 x 1023
1 dozen donuts is:
1 century is:
12
100 years.
1 millennium is:
1 mole is:
1000 years.
6.02 x 1023
particles/atoms/molecules
The Mole Concept
A mole:
The weight of 6.02 x 1023 atoms of
an element….a mole of different elements weighs
different amounts.
1 mole of Carbon:
1 mole of Calcium:
12.0 grams
40.1 grams
***The weight of 1 mole of an element
is known as its ATOMIC MASS***
A mole of a compound is an
observable quantity. It can be
weighed and used in experiments.

LEFT: Proceeding clockwise from the top, samples
containing one mole each of copper, aluminum, iron,
sulfur, iodine, and (in the center) mercury.

1 mole of hockey pucks would
equal the mass of the moon!

1 mole of basketballs would fill a
bag the size of the earth!
A. What is the Mole?

1 mole of pennies would cover the Earth 1/4 mile deep!
One mole = 6.02 x 1023 atoms,
molecules, or ions (Avogadro’s
number)

When coefficients are used to
balance chemical equations, they
express a mole-to-mole ratio of
the products and reactants.

These numbers do not
represent the exact
number of moles for the
reactants or products,
but rather give a ratio
we can use to compare
quantities.

Molar Mass
Mass of 1 mole of an element or
compound.

Atomic mass tells the...

atomic mass units per atom
(amu)
 grams per mole (g/mol)

Round to 1 decimal places

carbon
12.0 g/mol
aluminum
27.0 g/mol
zinc
65.4 g/mol



Molar Mass Examples

water
 H2O
 2(1.0) + 16.0 = 18.0 g/mol

sodium chloride
 NaCl
 23.0 + 35.5 = 58.5 g/mol
Molar Mass Examples
sodium bicarbonate

 NaHCO3
 23.0 + 1.0 + 12.0 + 3(16.0)
= 84.0 g/mol
sucrose
 C12H22O11
 12(12.1) + 22(1.0) + 11(16.0)

= 343.2 g/mol
Molar Mass Examples
molar
mass
6.02  1023
NUMBER
MASS
MOLES
IN
OF
PARTICLES
GRAMS
(g/mol)
(particles/mol)
Molar Conversions
Example 1
Convert 2.5 x 1025 atoms of Carbon into
moles.
2.5 x 1025 atoms
6.02 x 1023 atoms/mol
= 42 moles
Example 2
Convert 16.3 moles of Carbon dioxide (CO2)
into molecules.
16.3 moles
X
6.02 x 1023 molecules per mole.
= 9.81 x 1024 Molecules
Example 3
Convert 8.9 x 1024 molecules of Carbon
dioxide (CO2) into moles.
8.9 x 1024 Molecules
6.02 x 1023 Molecules/mol
= 14.78405316 moles
= 15 moles
X or ÷ ???
What units
do you
want?
Example 4 (YOU TRY)
Convert 28 moles of NaCl into molecules.
28 moles
X
6.02 x 1023 molecules per mole.
= 1.7 x 1025
Molecules
Avogradro’s Hypothesis
Avogradro’s Hypothesis
Avogradro hypothesized that equal volumes
of gas, at the same temperature and pressure
contain the same number of moles.
Avogradro’s Hypothesis
So…..
If 1 L of gas A reacts with 1L of gas B, then
the formula for the compound will be:
AB
If 2 L of gas A reacts with 1L of gas B, then
the formula for the compound will be:
A2B
Avogradro’s Hypothesis
If 2 L of gas A reacts with 3L of gas B, then
the formula for the compound will be:
A2B3
Avogradro’s Hypothesis
In other words, however many liters of a gas
you have that are in a reaction, the amount
(Liters) turns into the subscript.
***MAKE SURE ITS CONSTANT TEMP AND
PRESSURE OR IT DOESN”T WORK***
You Try
If 2 L of gas X contains 4 x 1023 molecules at
CONSTANT TEMP AND PRESSURE, how many
molecules will be present in 4 L of gas Z?
Double volume means double molecules.
(4 x 1023) x 2 = 8 x 1023 molecules.
What’s the formula of the resulting
compound?
X2Z4
Work Time
Questions:
Pg. 78 #s: 2,3,4,5