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Announcements. STUDY GROUPS- MEET NEXT WEEK HEADS-UP : EXAM #1 FRIDAY, SEPTEMBER 18 TH. How many C atoms are in a 0.96-carat diamond ring? (1 carat = 0.2g). 9.63 x 10 21 1.38 x 10 24 4.81 x 10 22 3.47 x 10 25. 20. Compounds and Moles.

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Announcements

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

  2. How many C atoms are in a 0.96-carat diamond ring? (1 carat = 0.2g) • 9.63 x 1021 • 1.38 x 1024 • 4.81 x 1022 • 3.47 x 1025 20

  3. Compounds and Moles • 1 mole of a compound contains 6.022 x 1023 molecules or “units” • Molar mass = sum of atomic molar masses • H2O • CO2 • Fe(NO3)3

  4. Examples to try(answers posted on web site under lecture notes) Consider UF6 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 UF6? How many F atoms in 0.5 mol UF6?

  5. Molecular vs. Nonmolecular compound terms • 1 mol CO2 contains 6.022 x 1023molecules • 1 mol NaCl contains 6.022 x 1023formula 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) • CuSO4 • Cu2SO4 • CuCO3 • Cu2CO3

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

  10. Empirical vs. Molecular Formulas • Formaldehyde • Empirical= CH2O • Molar mass of empirical formula= 30.03g/mol • Actual Molar mass= 30.03g/mol • Molecular= CH2O • Fructose • Empirical= CH2O • 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= C6H12O6

  11. Example 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?

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