1. Once you know the number of particles in a mole (Avogadro’s number = 6.02 x 10 23 ) and you can find the molar mass of a substance using the periodic table, you can use conversion factors to convert from grams to particles. Converting from Grams to Particles

2. Example How many particles of Fe are present in 48.23 grams of Fe? (what kind of particles are they?) First, find the molar mass of Fe from the periodic table and write the conversion factors. Hint: 1 mole = ? g 1 mole = ? Particles Set up the conversion problem!

3. Solution 1 mol Fe = 55.845 g 1 mol Fe = 6.02 x 10 23 atoms 48.23 g Fe x 1 mol x 6.02 x 10 23 atoms = 5.20 x 10 23 55.845 g 1 mol atoms Fe

4. Example You have a sample of FeCl 3 that has a mass of 85.23 g. How many chloride ions does the sample contain? 1 mol FeCl 3 = 3 mol Cl - ions 1 mol FeCl 3 = 162.20 g 85.23 g FeCl 3 x 1 mol x 3 mol Cl - x 6.02 x 10 23 ions = 162.20 g 1 mol FeCl 3 1 mol Cl - 9.49 x 10 23 ions

5. Example How many molecules of Br 2 are present in 35.85 grams? (why is this a molecule and not an atom?) 1 mol Br 2 = 159.80 g 1 mol Br 2 = 6.02 x 10 23 molecules 35.85 g Br 2 x 1 mol Br 2 x 6.02 x 10 23 molecules = 159.80 g 1 mol Br 2 1.35 x 10 23 molecules