1. STUDY GROUPS- MEET NEXT WEEK HEADS-UP : EXAM #1 FRIDAY, SEPTEMBER 18 TH Announcements

2. How many C atoms are in a 0.96-carat diamond ring? (1 carat = 0.2g) 1. 9.63 x 10 21 2. 1.38 x 10 24 3. 4.81 x 10 22 4. 3.47 x 10 25 20

3. Compounds and Moles 1 mole of a compound contains 6.022 x 10 23 molecules or “units” Molar mass = sum of atomic molar masses  H 2 O  CO 2  Fe(NO 3 ) 3

4. Consider UF 6 What is the molar mass? How many grams in 0.5 mol? How many molecules in 0.5 mol? How many U atoms in 0.5 mol of UF 6 ? How many F atoms in 0.5 mol UF 6 ? Examples to try (answers posted on web site under lecture notes)

5. Molecular vs. Nonmolecular compound terms 1 mol CO 2 contains 6.022 x 10 23 molecules 1 mol NaCl contains 6.022 x 10 23 formula units

6. Percent Composition The fraction of mass due to an element

7. Determining Formulas from % Composition The ratio of atoms in the formula is the same as the ratio of moles of those elements. If you determine the ratio of moles, you know the formula. However, the formula determined is the empirical formula.

8. Which of the following has the highest % composition of copper, Cu? (don’t calculate) 1. CuSO 4 2. Cu 2 SO 4 3. CuCO 3 4. Cu 2 CO 3

9. 1. 8.65g of iron combines with 3.72g of oxygen. What is the empirical formula of this compound? 2. Formaldehyde contains 40.0% C, 6.7% H, and 53.3% O. What is the empirical formula? Examples

10. Empirical vs. Molecular Formulas Formaldehyde  Empirical= CH 2 O  Molar mass of empirical formula= 30.03g/mol  Actual Molar mass= 30.03g/mol  Molecular= CH 2 O Fructose  Empirical= CH 2 O  Molar mass of empirical formula= 30.03g/mol  Actual Molar mass= 180.16g/mol  Divide actual molar mass by empirical formula mass to get multiplier: 180.16/30.03=6  Molecular= C 6 H 12 O 6

11. A hydrocarbon has 82.65%C and 17.34%H. The molar mass is 58.12 g/mol. What are the empirical and molecular formulas? Example