1. Unit 5: The Mole

2. Molar Mass
The sum of the atomic masses of all the atoms in the formula of a compound or molecule

3. Calculating Molar Mass
Calculate the molar mass for H2O:
H = 2 x g = g
O = 1 x g = g
Molar mass of water = g
Calculate the molar mass for Fe2(SO4)3:
Fe = 2 x g = g
S = 3 x g = g
O = 12 x g = g
Molar mass of iron (III) sulfate = g

4. Practice Practice Practice!!!

5. The Mole A counting word, just like a dozen
A mole = 6.02 x 1023
Two moles of marbles = 2 x 6.02 x 1023
Three moles of hair pins = 3 x 6.02 x 1023
6.02 x1023 also known as Avogadro’s #
Amedeo Avogadro (Italian Scientist) aided in this development

6. Mole Conversion Factor
Molar mass (g) of substance =
6.02 x 1023 molecules of substance =
1 mole of substance

7. Mole Conversion Factor Possibilities
molar mass (g)
6.02 x 1023 atoms or molecules

8. Mole Conversion Factor Possibilities
molar mass (g)
6.02 x 1023 atoms or molecules
Use the word atoms when describing a single element; use the word molecule when describing molecules and compounds

9. Mole Conversion Examples
Molar mass = Avogadro’s # = 1 mole
g of H2O = 6.02 x 1023 molecules of H2O = 1 mole of H2O
g of Fe2(SO4)3 = 6.02 x 1023 of Fe2(SO4)3 = 1 mole of Fe2(SO4)3
6.941 g of Li = x 1023 atoms of Li = 1 mole of Li

10. Mole Conversion Practice Problem 1
If 5,000,000 chlorine atoms are used to disinfect water, how many moles is that?
5,000,000 atoms Cl x mole Cl = 8.3 x 1023 mole Cl
6.02 x 1023 atoms Cl
8.3 x 1023 mole Cl  8 x 1023 mole Cl
Correct Sig Fig

11. Mole Conversion Practice Problem 2
Thirty moles of carbon monoxide could be a lethal amount. How many grams is that?
30 moles CO x g of CO = g of CO
1 mole CO
840.3 g CO  800 g CO
Correct Sig Fig

12. Mole Conversion Practice Problem 3
One liter of water weighs 1,000 g. How many water molecules is that?
1,000 g H2O x 1 mole H2O x 6.02 x 1023 molecules H2O = 3.3 x 1023 molecules H2O
g H2O mole H2O
3.3 x 1023 molecules H2O  3 x 1023 molecules H2O
Correct Sig Fig

13. Practice Practice Practice!!!