1. The Mole Notes

2. In every industry, there is a convenient way to measure a quantity of materials. For bakers, a baker’s dozen = 13 For egg farmers, a dozen = 12 For a ream of paper = 500 For a shoe salesman, a pair = 2 In chemistry, we find it convenient to measure out molecules in terms of a mole.

3. What is a mole?  A mole is the SI base unit for measuring the amount of a substance, or the number of molecules/atoms.  By definition, 1 mole will have 6.022 x 10 23 molecules/atoms or 602,200,000,000,000,000,000,0 00

4. WWe cannot count out 6.022 x 10 23 particles every time we want to use a mole of a substance. This is where math and conversion skills can help… we can mathematically convert moles of a substance into grams of a substance (using dimensional analysis or t charts) and then weigh out one mole using a balance. TThis would be similar to the way Chuck E Cheese determines how many tickets you have for a prize. Instead of counting, the machines weigh them.

5. MEMORIZE THESE! Conversion factors:  1 mole = 6.022 x 10 23 atoms/molecules  1 mole = atomic/molecular mass of a atom/molecule in grams  1 mole = 22.4 L of a molecule

6. Molar Mass  the mass in grams of one mole of atoms or molecules. The units are g/mol.

7. Example 1  How many grams will 1 mole of H 2 O weigh? Since 1 mole = molecular mass of a molecule in grams then 2(1) + 16 = 18 amu. If I have a mole of water, then it will weigh 18 g

8. Example 2  How many moles are in 36g of H 2 O? Since I know 1 mole of H 2 O is 18g then 36g H2O 18g H2O 1 mole H2O = 2 mole H2O

9. Example 3  How many grams are in 2 moles of Al(OH) 3 ? First calculate molar mass = 27 + 3 (16) + 3 (1) = 27 + 48 + 3 = 78 g/mol 2 moles Al(OH) 3 1 mole Al(OH) 3 78g Al(OH) 3 = 156 g of Al(OH)3

10. Example 4  How many molecules are in 2 mol H 2 O? Since 1 mole = 6.022 x 10 23 atoms/molecules if I have 2 moles then I must have 2(6.022 x 10 23 )= 1.204 x 10 24

11. How to use calculator  To input the # 6.02 x 10 23 into the calculator 1 – type in 6.02 and then hit “2 nd ” (it’s blue) and then the “X -1 ” button Then enter the 23 (do not enter x10!!!)