The Mole Road Map
Chemistry
Unit 6: Chemical Quantities
Lecture 6.4
Objectives
• Convert a quantity of a chemical between
moles, mass (g), particles, and volume.
ALL About the Mole…
• We have now looked at the mole in terms
of mass (g), particles, and volume.
• HOWEVER…in order to do these
conversions, one of our units had to be the
mole.
• What do you do, if you are asked to
convert between two units and neither one
is mole?
Everything Goes Through The
Mole!
• To convert from one unit to another, you
must use the mole as an intermediate
step.
• In other words…you might need a “twostep” conversion problem.
What is a “Two-Step” Conversion
Problem?
• Two conversion factors
– One to convert from given unit to moles
– One to convert from moles to wanted unit
Mole Road Map
Volume
of gas
22.4 L
1 mol
(STP)
Mass
(grams)
22.4 L
1 mol
Mole
Representative
Particles
(atoms, molecules, or formula units)
Here’s An Example
Calculate the number of molecules in 60.0 g NO2.
Given: 60.0 g NO2
1st Equality:
Molar Mass Equality
molar mass NO2 : 46.01 g
46.01 g = 1 mol
2nd Equality:
Definition of Mole Equality
1 mol = 6.02 x 1023 molecules
So here’s the equation:
60.0 g NO2
1
x
1 mol x 6.02 x 1023 molecules =
46.01 g NO2
1 mol
7.85 x 1023 molecules NO2
Another Example
Calculate the volume, in liters, of 3.24 x 1022
molecules of Cl2 (STP).
3.24 x 1022 molecules Cl2 x
1 mol
x 22.4 L Cl2 =
1
6.022 x 1023 molecules
1 mol
1.21 L Cl2
What Now?
• You will NOT be allowed to use your
“Road Map” on the test, so you need to
practice enough that you no longer rely on
it to help you through solving these
problems.