1. The Mole: The SI(metric) unit to measure the amount of a substance.

2. The Mole Scientists set out to develop a basic unit of measurement to convert from atoms to grams to make obtaining samples easier and more standard. Carbon-12 was used to set the standard, one mole C = the number of atoms of C in 12 grams of C-12. Experiments show that there are 6.02 x 10 23 carbon atoms in 12 grams of Carbon-12. 6.02 x 10 23 things is a “mole” of any thing!

3. Avogadro: scientist who determined the number of “things” in a mole. –Can be used to measure atoms, molecules, or formula units.

4. Conversion Factors: 1 mole = Avogadro’s number of anything else or 1 mole = 6.02 x 10 23 atoms/molecules/Formula units 1 mole = molar mass (g)

5. Steps for conversions: 1 st choose which conversion factor you need. –1mol = molar mass (g) –1 mol = 6.02 x 10 23 2 nd place the number in the problem over one, and apply conversion factor so units are diagonal. 3 rd multiply across the top & bottom, then divide the top by the bottom.

6. Practice How many moles are in 35.24 g NaCl? How many atoms are in 74.2 moles MgO?

7. Practice: How many molecules are in 17.4 moles H 2 ? What is the mass of 42.3 moles of Ca 3 N 2 ?

8. 2 step problems: How many grams are in 4.3 x 10 24 formula units of AlCl 3 ? How many atoms are in 76.5 g FeO?