Unit 7: Chemical
Quantities
Moles <--> Particles
After today, you will be able to…
• Using dimensional analysis, calculate
how many atoms, molecules, or
formula units are in one mole of that
substance
• Use correct significant figures and
units in these calculations
• Identify key scientists in the
development of the mole
Substances can be measured
in different ways….
The
Mole
can
be
1.Count – 5 apples, dozen eggs
related
each16oz
of
2.Mass
– 2lbs ofto
bananas,
box of cereal
these types of
3.Volume – gallon of milk, pint of
measurements.
cream
A Brief History on the Mole…
Avogadro: (1811) An Italian
scientist who studied the
behavior of gases.
Theorized:“The volume of a
gas at a specific temperature
and pressure contains equal
numbers of atoms or molecules
regardless of the nature of the
gas.”
Loschmidt (1865): Estimated the
average diameter of the molecules
in air and was able to calculate the
number of particles in a given
volume of gas.
Millikan (1910): Measured the
charge on an electron. From
the charge on a mole of
electrons, he divided the
two and obtained Avogadro’s
number.
Perrin (1926): Earned the
Nobel Prize for computing
Avogadro’s number using many
different methods and named
this constant in honor of
Avogadro. Used oxygen as a
standard and proposed
“Avogadro’s number is the
number of molecules in exactly
32-grams of oxygen.”
The standard was later changed to
the carbon-12 isotope.
The presently accepted definition of
the mole is:
“The amount of any substance that
contains as many elementary
entities as there are in 12 grams of
pure carbon-12.”
The mole (mol) as a unit in
chemistry serves as a bridge
between the atomic and
macroscopic worlds.
In Latin, mole means
“huge pile.”
1 mole =
23
6.02x10
atoms, molecules, or formula units
= 602,000 ,000,000,000,000,000 ,000
= six-hundred and two sex-tillion
This equality can be used as
a conversion factor to
convert particles into moles,
or moles into particles.
Example: How many atoms are in a
1.22 mole sample of sodium?
K: 1.22 mol Na
U: ? atoms Na
K stands for what we know!
U stands for what we are solving for!
1.22 mol Na x 6.02x1023 atoms Na =
1
1 mol Na
7.34x1023 atoms Na
Example: How many moles are
equal to 4.79x1024 molecules of CO?
K: 4.79x1024 molec. CO
U: ? mol CO
4.79x1024 molec. CO x
1 mol CO
. =
6.02x1023 molec. CO
1
7.96 mol CO