1. Basics of Moles

2. Molar mass Molar masses, atomic weights/masses, molecular weights/masses, formula weights/masses: all mean the same Calculate by adding the atomic masses of every atom in the formula – NaCl: 23.00 + 35.45 – NH 4 OH: 14.01 + (4 x 1.008) +16.00 + 1.008 – Ca(NO 3 ) 2 40.08 + (2 x 14.01) + (6 x 16.00)

3. Percent composition Mass of what you are talking about divided by mass of molecule Example: percent nitrogen in sodium nitrate – Na: 22.99 – N: 14.01 – O: 3 x 16.00 = 48.00 – Total 85.00 % N is (14.01/85.00) x 100 = 16.5%

4. Empirical formulas Lowest ratio of subscripts Note how to calculate empirical formulas – Convert % to g – Divide each by its molar mass – Divide each by smallest – Results should be whole number +/- 0.2 – If a result rounds to X.5, multiply each subscript by 2

5. Molecular formulas A whole number “multiple” of an empirical formula Divide given molar mass by empirical formula’s molar mass Multiply each subscript by this value.

6. The mole 1 mole = 6.022 x 10 23 of whatever you are dealing with. – 1 mole of gold atoms = 6.022 x 10 23 gold atoms – 1 mole sugar molecules = 6.022 x 10 23 sugar molecules – 1 mole of poodles = 6.022 x 10 23 poodles View a mole the same way you would a dozen: – A dozen means 12 – A mole means 6.022 x 10 23 6.022 x 10 23 is called Avogadro’s number

7. Molar mass The molar mass is the average atomic mass, so that is the number of grams in 1 mole of whatever you are talking about. 1 mole of carbon atoms = 6.022 x 10 23 carbon atoms and has a mass of 12.01 g 1 mole of aluminum atoms = 6.022 x 10 23 Aluminum atoms and has a mass of 26.98 g

8. Converting grams to moles Grams divided by molar mass = moles

9. Converting moles to grams Moles times molar mass = grams

10. Converting moles to particles Particles may be atoms, ions, molecules, or poodles. Moles times Avogadro’s number = particles

11. How to make the math easy Moles x 6.022 Write this answer x 10 23 Convert to scientific notation Example 2.3 moles = ? Particles – 2.3 x 6.022 = 13.85 – 13.85 x 10 23 – 1.385 x 10 24

12. Converting particles to moles Particles may be atoms, ions, molecules, or poodles. Particles divided by Avogadro’s number = moles

13. How to make the math easy Divide first part of particles number by 6.022 Particles exponent – 23 = answer exponent Convert to scientific notation Example: 1.385 x 10 24 particles is ? Moles 1.385/ 6.022 = 0.23 24-23 = 1 Therefore: 0.23 x 10 1, or 2.3 x 10 0, or 2.3