Introduction to Moles
Part I: Count the number of Atoms
Example: CH4 C=1 atom and H =4 atoms
 Additional examples will be observed in class
 The red 4 is a subscript indicating 4 atoms in this case
 If no subscript is seen the subscript is 1
Part II: Formula Mass/Molar Mass
 You find both the same way, the only difference is the units
o Formula Mass units = amu (atomic mass units)
o Molar Mass units = g/mol (grams per mole)
 What is a mole?
 1 mole is = to the amount of grams in the Molar mass of any substance
 1 mole is also = to the number of particles (also known as atoms,
formula units, or molecules) in a substance = 6.022 x 1023 (Avogadro’s
number is a constant)
 You need to count the atoms and then find the atomic mass of each element in the substance,
multiple each and then add the totals
Example: C6H12O6
C: 6 atoms x 12(atomic mass) = 72
H: 12 atoms x 1 (atomic mass) = 12
O: 6 atoms x 16 (atomic mass) = 96
Formula Mass = 180 amu
Molar Mass = 180 g/mol
Part III: Mole problem formulas: Examples will be seen in class
1. Moles to Mass: Given moles x molar mass of given ÷ 1 mole
2. Mass to Moles: Given mass x 1 mole ÷ molar mass of given
3. Moles to particles (remember particles have other names: atoms, formula units, or molecules)
Given moles x 6.022 x 1023 particles ÷ 1 mole
4. Particles to Moles: Given particles x 1 mole ÷ 6.022 x 1023 particles
5. Mass to Particles: (two steps-can’t go directly from mass to particles nor particles to mass)
Given mass x 1 mole/molar mass of given X 6.022 x 1023 particles/1 mole
6. Particles to Mass: (two steps again) Given particles x 1 mole
Given particles x 1 mole /6.022 x 1023 particles X molar mass of given/1 mole