1. Factor-Label Method Math technique used for conversion problems. Not the same as the proportion technique. More powerful in multistep problems.

2. Changing Units In the factor-label method, you use a conversion factor to express the quantity in the desired units. Set up your calculation so the units cancel out.

3. If you have 8 dozen eggs, how many eggs do you have? 8 Doz eggs X 12 eggs = 96 eggs 1 Doz eggs That’s the conversion factor.   That’s the given information.  That’s the answer.

4. Another Example of the Factor- Label Method How many quarts are in 3.5 gallons? Equality you know: 1 gallon = 4 quarts. Format = Given X Conversion Factor = AnsFormat = Given X Conversion Factor = Ans Conversion Factor is a ratio built from the equalities. You put it together so the units cancel out. The value of the ratio is “one.”

5. Gallons to Quarts 3.5 Gallons X 4 Quarts = 14 Quarts 1 Gallon Identify the given, the conversion factor, and the answer.

6. Number of Moles in Sample The mass of an iron bar is 27.9 g. How many moles of Fe are in the sample? What equalities do you know? –1 mole of Fe = –55.8 g Fe = 23 –6.02 X 10 23 atoms Fe

7. formula mass 6.02 X 10 23 22.4 L/mol

8. Factor-Label Method Format = Given X Conversion Factor = Ans 27.9 g Fe X 1 Mole Fe = 0.5 Mole Fe 55.8 grams Fe

9. Formula Mass of a Compound Sum of the atomic masses for all the atoms present. CO 2 has a formula mass of: 12.0 amu + 16.0 amu + 16.0 amu = 44.0 amu

10. Molar Mass of any Compound = Formula mass expressed in grams. 1 mole of NaCl = 58.5 grams NaCl 1 mole of CO 2 = 44.0 grams of CO 2 1 mole of H 2 O = 18.0 grams of H 2 O 1 mole of CaCO 3 = 100. grams of CaCO 3 1 mole of LiF = 25.9 grams of LiF

11. Mole  Mass Conversions Conversion factor comes from an equality you build from the periodic table.

12. Mole - # of particle Conversions 1 equality, so it’s easier. 1 mole of anything = 6.02 X 10 23 of that thing

13. Mole - # of Particle Conversions How many particles are in 3 moles of He? Given = 3 moles of He Equality: 1 mole of He molecules = 6.02 X 10 23 molecules of He Format: Given X Ratio = Ans 3 moles He molecules X 6.02 X 10 23 molecules = 1 mole of He molecules

14. 18 X 10 23 molecules!

15. # of Particles to Moles How many moles are in 3.01 X 10 23 particles of Ar? Given: 3.01 X 10 23 particles of Ar Equality: 1 mole = 6.02 X 10 23 particles 3.01 X 10 23 particles X 1 mole = 6.02 X 10 23 particles

16. 0.5 moles!