2. WHAT IS A MOLE? SI unit for Amount of Substance

3. A mole is a unit like “dozen” or “pair” or “gross”. It doesn’t represent a measured number, but a counted number. A dozen is 12. A pair is 2. A gross is 144. A mole is 6.02 x 10 23*** particles. Like a dozen and a gross, it can be 6.02 x 10 23 of anything, but in chemistry we are usually talking about (atoms, ions, molecules, formula units).

4. The mole is important because it represents a practical amount of a substance for use in the lab or in calculations. Keep in mind that a mole of water is only 18.02 mL of water! (1 gram water = 1 mL) Amadeo Avogadro is credited with determining the value of the mole that is accepted today(1 mole = 6.02 x 10 23 ). He also determined that one mole of any gas will occupy a volume of 22.4 liters at STP.

5. One mole of any substance contains 6.02 x 10 23 particles of that substance. The mass of one mole of any substance is equal to its molar mass in grams. We can use the average atomic mass of an element as its molar mass, which is provided for us on the periodic table – isn’t chemistry great! 1 mole of carbon = 6.02 x 10 23 atoms of carbon = 12.01 g of carbon 1 mole of NaCl = 6.02 x 10 23 formula units of NaCl = 58.44 g of NaCl 1 mole of O 2 = 6.02 x 10 23 molecules of O 2 = 32.00 g of O 2 = 22.4 L of O 2

6. Molar Mass – mass found by adding the molar mass of the atoms in a molecule. - important calculation because we do not have a mole meter, so in order to talk about moles in a laboratory situation, we measure the mass and convert to moles *steps for calculating molar mass: 1. list & count the atoms 2. multiply the number of atoms by the molar mass from the periodic table 3. add the total mass of each element ex) NaCl Na – 1 x 22.99 g = 22.99 g Cl – 1 x 35.45 g = 35.45 g 58.44 g= 1 mole NaCl

7. (NH 4 ) 3 PO 4 Calculate Molar Mass N – 3 x 14.01 g = 42.03 g H – 12 x 1.01 g = 12.12 g P – 1 x 30.97 g = 30.97 g O – 4 x 16.00 g = 64.00 g 149.12 g= 1 mole (NH 4 ) 3 PO 4

8. Molar Volume – the volume occupied by one mole of a any gas at STP= 22.4 L ex) 1 mole CO 2 = 6.02 x 10 23 molecules of CO 2 = 44.01 g of CO 2 = 22.4 L of CO 2 at STP

9. Mole Conversions - You must be able to convert from grams to moles to particles to volume in any combination for any element or compound! A helpful hint to remember is that, in this unit, 1 always goes with mole!

10. Ex) How many grams are in 3 moles of water? ?g = 3 mol H2O x 18.02 g/1 mol = 54.06 g H2O Ex) How many moles are in 88.02 g of carbon dioxide? ?mol = 88.02 g CO2 x 1 mol/44.01 g = 2 mol CO2 Ex) What volume will 2 moles of carbon dioxide occupy at STP? ?L = 2 mol CO2 x 22.4 L/1 mol = 44.8 L CO2

11. CHEMISTRY Rocks! Yeah Smile lots!