2. IIIIIIIV The Mole I. Molar Conversions

3. What is the Mole? A counting number (like a dozen or a pair) Avogadro’s number 6.02  10 23 1 mole = 6.02  10 23 things. (things can be atoms, molecules, formula units) A large amount!!!!

4. 1 mole of hockey pucks would equal the mass of the moon! A. What is the Mole? 1 mole of pennies would cover the Earth 1/4 mile deep! 1 mole of basketballs would fill a bag the size of the earth!

5. Example n How many molecules are in 2.50 moles of C 12 H 22 O 11 ? 2.50 mol 6.02  10 23 molecules 1 mol = 1.51  10 24 molecules C 12 H 22 O 11

6. Mole- Volume n At the same temperature:  Equal volumes of gases contain equal numbers of moles n STP  Standard temperature and pressure  1 mole of any gas at STP has a volume of : 22.4 L

7. Example n How many moles of neon are in 44.8L of neon at STP? 44.8 L 1 mol 22.4 L = 2 mol

8. Molar Mass How much do I weigh??

9. Molar Mass n Mass of 1 mole (6.02 X 10 23 atoms or molecules) of an element or compound. n Atomic mass tells the...  atomic mass units per atom (amu)  grams per mole (g/mol) n Round to 2 decimal places when calculating

10. Molar Mass Examples This is easy! Just look at the periodic table! Phosphorus Aluminum Helium Silver 30.97 g/mol 26.98 g/mol 4.00 g/mol 107.87 g/mol

11. Molar Mass Examples WATER: H2OH2O  Ca(OH) 2 Ca  40.08 + O  2(16) + H  2(1.01) = 74.10 g/mol H → O → = 2.02 g/mol 2 x 1.01 g/mol 1 x 16.0 g/mol = 16.0 g/mol 18.02 g/mol

12. Molar Mass n sodium bicarbonate n sucrose  NaHCO 3  84.01 g/mol  C 12 H 22 O 11  342.34 g/mol

13. Example n How many moles of carbon are in 26 g of carbon? 26 g C 1 mol C 12.01 g C = 2.2 mol C

14. Examples n Find the mass of 2.1  10 24 molecules of NaHCO 3. 2.1  10 24 molecules 1 mol 6.02  10 23 molecules = 290 g NaHCO 3 84.01 g 1 mol

15. A. Percentage Composition n the percentage by mass of each element in a compound

16.  100 = A. Percentage Composition %Cu = 127.10 g Cu 159.17 g Cu 2 S  100 = %S = 32.07 g S 159.17 g Cu 2 S 79.852% Cu 20.15% S n Find the % composition of Cu 2 S.

17. %Fe = 28 g 36 g  100 = 78% Fe %O = 8.0 g 36 g  100 = 22% O n Find the percentage composition of a sample that is 28 g Fe and 8.0 g O. A. Percentage Composition

18. n How many grams of copper are in a 38.0-gram sample of Cu 2 S? (38.0 g Cu 2 S)(0.79852) = 30.3 g Cu Cu 2 S is 79.852% Cu A. Percentage Composition

19. IIIIIIIV The Mole Empirical/Molecular Formulas

20. B. Empirical Formula C2H6C2H6 CH 3 reduce subscripts n Smallest whole number ratio of atoms in a compound

21. Empirical Formula 1. Find mass (or %) of each element. (may be given) 2. Find moles of each element. (g to moles) 3. Divide moles by the smallest # to find subscripts. 4. When necessary, multiply subscripts by 2, 3, or 4 to get whole #’s.

22. Empirical Formula n Find the empirical formula for a sample of 25.9% N and 74.1% O. 25.9 g 1 mol 14.01 g = 1.85 mol N 74.1 g 1 mol 16.00 g = 4.63 mol O 1.85 mol = 1 N = 2.5 O

23. Empirical Formula N 1 O 2.5 Need to make the subscripts whole numbers  multiply by 2 N2O5N2O5

24. Examples n An organic compound is found to contain 92.25% carbon and 7.75% hydrogen. Determine the empirical formula.  Empirical Formula: CH n What is the empirical formula of a compound that contains 53.73% Fe and 46.27% S?  Empirical Formula: Fe 2 S 3

25. Molecular Formula n “True Formula” - the actual number of atoms in a compound CH 3 C2H6C2H6 empirical formula molecular formula ?

26. C. Molecular Formula 1. Find the empirical formula. 2. Find the empirical formula mass. 3. Divide the molecular mass by the empirical mass. 4. Multiply each subscript by the answer from step 3.

27. Molecular Formula n The empirical formula for ethylene is CH 2. Find the molecular formula if the molecular mass is 28.1 g/mol? 28.1 g/mol 14.03 g/mol = 2.00 empirical mass = 14.03 g/mol (CH 2 ) 2  C 2 H 4