Unit 7: Chemical
Quantities
2-Step Conversions
After today, you will be able to…
• Perform two-step conversions
using molar mass and
representative particles (atoms,
molecules, and formula units)
We have already learned…
How to convert moles into
particles and vice versa by
using the conversion factor…
1 mole = 6.02x1023 particles
How to convert moles into
grams and vice versa by using
the conversion factor…
1 mole = atomic mass
in grams
These two conversion factors
can now be combined…
Particles  Moles  Grams
6.02x1023
molar mass
Grams  Moles  Particles
molar mass
6.02x1023
Example: What is the mass of
1.79x1024 formula units of K3PO4?
K: 1.79x1024 F.U. K3PO4
U: ? g K3PO4
1.79x1024 F.U. K3PO4 x
1
3 K = 3(39.10) =
1 P = 1(30.97) =
4 O = 4(16.00) =
117.30
30.97
+64.00
212.27
1 mol K3PO4
x 212.27 g K3PO4 =
6.02x1023 F.U. K3PO4
1 mol K3PO4
.
.
631 g K3PO4