What is a mole?• A mole is a quantity equal to the number of

atoms in exactly 12g of carbon-12. Remember that the relative atomic mass is always based on the

comparison of any atom to the carbon atom.

I say dozen, you say…Molar Mass Dozar Mass

# of dozens

# of eggs

Mass of egg

Mass of dozen

What is its symbol?

• Symbol: mol

• 12g of C-12 = 1 mol of C-12

• The Atomic mass of C-12 = 12 amu = 12g/mol

This is called the MOLAR MASS

The molar mass of a substance is…?

…the mass of one mole of that substance.

Substance Relative Atomic Mass (amu)

Molar Mass (g/mol)

Carbon (C) C = 12.01 12.01

Neon (Ne) Ne = 20.18 20.18

Calcium (Ca) Ca = 40.08 40.08

1 mole of CO2 has a mass of 44 amu…

What is really in 1 mol?

Avogadro’s number represents…

… The number of entities in 1 mol. – There are always 6. 02 X 1023 atoms or molecules

in 1 mol.

1. Change 4.0 X 103 Na atoms to mass of sodium atoms.

2. Change 55g of Ca(OH)2 to molecules of Ca(OH)2.

Name Formula

Beryllium Chloride BeCl2

Diphsphorous pentoxide P2O5

Sodium carbonate Na2CO3

Magnesium nitride Mg3N2

Sulfur trichloride SCl3

Iron (2) phosphate Fe3(PO4)2

Calcium nitrate Ca(NO3)2

Aluminum sulfide Al2S3

Lead (4) fluoride PbF4

Complete Part B on your own