1. THE MOLE Measuring Matter

2. What is a mole? In Chemistry, a mole is the unit used to measure the amount of a substance represented by the coefficient in a chemical reaction usually abbreviated as mol one mole of any substance is equal to 6.02 X 10 23 particles of that substance 1 mol = 6.02 X 10 23 particles 2Mg + O 2 2MgO

3. What is 6.02 X 10 23 ?? 6.02 X 10 23 is called Avogadro’s number and is equal to: 6.02 X 10 X 10 X 10 X 10 X 10 X 10 X 10 X 10 X 10 X 10 X 10 X 10 X 10 X 10 X 10 X 10 X 10 X 10 X 10 X 10 X 10 X 10 X 10 Or 602,000,000,000,000,000,000,000 Amadeo Avogadro was an Italian physicist who determined the volume of one mole of a gas in 1811

4. Mass and the Mole The mass, in grams, of one mole of any substance is equal to its atomic mass (or the sum of the atomic masses in a compound). called the molar mass expressed in units of grams/mole (g/mol) Example: An atom of manganese (Mn) has an atomic mass of 54.94 amu. The molar mass of manganese is 54.94 g/mol.

5. Using a conversion factor to convert from moles to mass How many grams of chromium (Cr) are there in 0.0450 moles of that element? Cr Chromium 24 52.00 1)From the Periodic Table, find the atomic mass of chromium. molar mass Cr = 52.00 g/mol atomic mass Cr = 52.00 amu 52.00 g Cr 1 mol Cr 0.0450 mol Cr X 52.00 g Cr 1 mol Cr = 2.34 g Cr 2) Determine the molar mass of chromium. 3) Create a conversion factor to do your calculations

6. Converting from mass to moles In our previous example we converted 0.0450 mol Cr to grams of Cr using the conversion factor: 52.00 g Cr 1 mol Cr What conversion factor would we use if we were trying to convert a known mass (in grams) of Cr to moles? 1 mol Cr 52.00 g Cr

7. Calcium (Ca) is the fifth most abundant element on earth. How many moles of calcium are there in 525 g Ca? Ca Calcium 20 40.08 Atomic mass Ca = 40.08 amu Molar mass Ca = 40.08 g/mol 525 g CaX 1 mol Ca 40.08 g Ca = 525 mol Ca 40.08 =13.1 mol Ca

8. Practice 1)How many moles of Silver (Ag) are there in 25.5 g Ag? 2)Determine the mass, in grams, of 3.45 mol Cobalt (Co) BONUS for the REAL thinker: How many atoms of gold (Au) would there be in 25.0g of the metal? 0.236 mol Ag 203 g Co 7.65 X 10 22 atoms Au How did the REAL thinkers get this?