Molar Mass

1
Molar Mass
2
Why 6.02 X 1023?

• Couldnt Avogadro have picked an easier number to
  work with??
• It has been determined experimentally that there
  are 6.02 X 1023 carbon atoms in 12 g of C-12.
• 1 atom of C-12 has a mass of 12 u
• 1 mole of C-12 has a mass of 12 g
• The mole allows us to easily convert from atomic
  mass units (microscopic) into grams (macroscopic)

3

• 1 C-12 atom has a mass of 12 u
• 1 mole of C-12 has a mass of 12 g
• OR 12 g/mole
• 1 O-16 atom has a mass of 16 u
• 1 mole of O-16 has a mass of 16 g
• OR 16 g/mole
• This applies to molecules as well
• 1 molecule of H2O 2 X1.01 u 16.00 u 18.02 u
• 1 mole of H2O 18.02 g
• OR 18.02 g/mole

4
Molar Mass

• The mass of 1 mole of any substance is called its
  molar mass and it is written in units of g/mol
• E.g. The molar mass of potassium is 39.10 g/mol
  (i.e 6.02X 1023 atoms of K have a mass of 39.10
  g)
• Dont forget about diatomic molecules!!
• The molar mass of an oxygen atom (O) is 16.00
  g/mol. The molar mass of oxygen molecules (O2) is
  32.00 g/mol (16.00 X 2)

5
E.g. What is the molar mass of ammonium
phosphate?
6
Practice

• What does a mole looks like?
• Worksheet
• P. 170 7-13
• P. 171 1-5