The Mole and Chemical Composition Notes
The Mole:

The amount of substance that contains as many particles as there are atoms in exactly 12 g of
carbon.

We can think of the mole as a counting unit for chemists.
 Other Examples of counting units:
 1 dozen donuts = 12 donuts
 1 ream of paper = 500 sheets
Avogadro’s Number:

Is the number of particles in exactly one mole of a pure substance.

6.02 x 1023 is called “Avogadro’s Number” in honor of the Italian chemist Amadeo Avogadro
(1776-1855).

That is 602000000000000000000000 atoms in 1 mole of a substance; THAT’S A GIGANTIC
NUMBER!!!!!!!!!
Molar Mass:

Is the mass of 1 mole of a per substance

Has units of grams per mole (g/mol)

Equaled to the atomic mass of the element or compound.
Molar Mass of a Compound:

Add up all the masses of each type of atom in the compound.

Example: Determine the molar mass of Ca(OH)2

You would add up the mass of ONE calcium (approx. 40 g/mol), mass of TWO oxygens
(approx.. 16 g/mol), and the mass of TWO hydrogens (approx. 1 g/mol)
Ca: 1 x 40 = 40 g/mol
O: 2 x 16 = 32 g/mol
H: 2 x 1 =
The molar mass is equaled to the sum: 74 g/mol.
2 g/mol
Practice: Determine the molar mass of Cu(NO3)2
Notice the Units!
The Mole and Chemical Composition Notes
Calculations:
Converting moles to grams
Given moles 
Obtain the grams of substance from
the periodic table. This is the molar
mass!
grams of substance
 g of substance
1 mol
Converting grams to moles
Given grams 
1 mol
 moles of substance
grams of substances
Obtain the grams of substance from
the periodic table. This is the molar
mass!
Converting moles to particles (atoms/molecules/ions)
6.02 x 10 23 particles
Given moles 
 particles of a substance
1 mol
Converting particles (atoms/molecules/ions) to moles
Given particles 
1 mol
 mol of a substance
6.02  10 23 particles
Converting grams to particles (atoms/molecules)
Given grams 
1 mole
6.02  10 23 particles

 particles of a substance
grams of a substance
1 mole
Obtain the grams of substance from
the periodic table. This is the molar
mass!
Converting particles (atoms/molecules) to grams
Given particles 
Obtain the grams of substance from
the periodic table. This is the molar
mass!
1 mol
grams of substance

 grams of a substance
23
1 mol
6.02  10 particles