1. Unit 6: Stoichiometry Section 2: Moles, Masses, and Molecules, OH MY!!!!!

2. The Mole A counting unit, just like a dozen –A dozen = 12 –A mole = 6.02 x 10 23 Two moles of marbles = 2 x 6.02 x 10 23 Three moles of Koa trees= 3 x 6.02 x 10 23 6.02 x10 23 is known as Avogadro’s # –Amedeo Avogadro (Italian Scientist) aided in this development

3. Molar Mass The sum of the atomic masses of all the atoms in a formula; equals the mass of one mole of the substance.

4. Calculating Molar Mass Calculate the molar mass of H 2 O: –H = 2 x 1.0079 g = 2.0158 g –O = 1 x 15.999 g = 15.999 g Molar mass of water = 18.0148 g Calculate the molar mass for Fe 2 (SO 4 ) 3 : –Fe = 2 x 55.847 g = 117.694 g –S = 3 x 32.06 g = 96.18 g –O = 12 x 15.999 g = 191.988 g Molar mass of Iron (III) sulfate = 405.862 g

5. Mole Conversion Factor 1 mole of a substance = Molar mass of a substance = 6.02 x 10 23 molecules of a substance

6. Mole Conversion Factor Possibilities 1 mole molar mass (g) 1 mole 6.02 x 10 23 atoms or molecules 1 mole

7. Mole Conversion Factor Possibilities molar mass (g) 6.02 x 10 23 atoms or molecules molar mass (g)  The word atoms = single element; The word molecules = multiple atoms in a formula.

8. Mole Conversion Examples Molar mass = Avogadro’s #= 1 mole 18.0148 g of H 2 O = 6.02 x 10 23 molecules of H 2 O = 1 mole of H 2 O 405.862 g of Fe 2 (SO 4 ) 3 = 6.02 x 10 23 of Fe 2 (SO 4 ) 3 = 1 mole of Fe 2 (SO 4 ) 3 6.941 g of Li = 6.02 x 10 23 atoms of Li = 1 mole of Li

9. 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 1 mole Cl = 8.3 x 10 -18 mole Cl 6.02 x 10 23 atoms Cl 8.3 x 10 -18 mole Cl  8 x 10 -18 mole Cl Correct Sig Fig = the same as the given number in the problem with the lowest number of sig figs (i.e. “5,000,000”)

10. Mole Conversion Practice Problem 2 Thirty moles of carbon monoxide could be a lethal amount. How many grams is that? 30 moles CO x 28.01 g of CO = 840.3 g of CO 1 mole CO 840.3 g CO  800 g CO Correct Sig Fig

11. Mole Conversion Practice Problem 3 One liter of water has a mass of 1,000 g. How many water molecules is that? 1,000 g H 2 O x 1 mole H 2 O x 6.02 x 10 23 molecules H 2 O = 3.3 x 10 25 molecules H 2 O 18.0148 g H 2 O 1 mole H 2 O 3.3 x 10 25 molecules H 2 O  3 x 10 25 molecules H 2 O Correct Sig Fig