1. Slide 1 of 40 © Copyright Pearson Prentice Hall Percent Composition and Chemical Formulas > The Percent Composition of a Compound The percent by mass of an element in a compound is the number of grams of the element divided by the mass in grams of the compound, multiplied by 100%. 10.3

2. Slide 2 of 40 © Copyright Pearson Prentice Hall Percent Composition and Chemical Formulas > The Percent Composition of a Compound I. Percent Composition from Mass Data 10.3

3. © Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 3 of 40 10.9

4. © Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 4 of 40

5. © Copyright Pearson Prentice Hall Slide 5 of 40 Practice Problems for Sample Problem 10.9

6. Slide 6 of 40 © Copyright Pearson Prentice Hall Percent Composition and Chemical Formulas > The Percent Composition of a Compound II. Percent Composition from the Chemical Formula 10.3

7. © Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 7 of 40 10.10

8. © Copyright Pearson Prentice Hall Slide 8 of 40 Practice Problems for Sample Problem 10.10

9. Slide 9 of 40 © Copyright Pearson Prentice Hall Percent Composition and Chemical Formulas > The Percent Composition of a Compound Percent Composition as a Conversion Factor You can use percent composition to calculate the number of grams of any element in a specific mass of a compound. 10.3

10. Slide 10 of 40 © Copyright Pearson Prentice Hall Percent Composition and Chemical Formulas > The Percent Composition of a Compound Propane (C 3 H 8 ) is 81.8% carbon and 18% hydrogen. You can calculate the mass of carbon and the mass of hydrogen in an 82.0 g sample of C 3 H 8. 10.3

11. Slide 11 of 40 © Copyright Pearson Prentice Hall Percent Composition and Chemical Formulas > Empirical Formulas The empirical formula gives the lowest whole- number ratio of the atoms of the elements in a compound. 10.3

12. Slide 12 of 40 © Copyright Pearson Prentice Hall Percent Composition and Chemical Formulas > Empirical Formulas Ethyne (C 2 H 2 ) is a gas used in welder’s torches. Styrene (C 8 H 8 ) is used in making polystyrene. These two compounds of carbon have the same empirical formula (CH) but different molecular formulas. 10.3

13. Slide 13 of 40 © Copyright Pearson Prentice Hall Percent Composition and Chemical Formulas > Rules for Determining Empirical Formula: 1.Convert grams of each element to moles 2.Divide each # of moles by the smallest # of moles 3.If answers to #2 are not all whole numbers, multiply by integers (2, 3…) to get whole numbers

14. © Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 14 of 40 10.11

15. © Copyright Pearson Prentice Hall Slide 15 of 40 Practice Problems for Sample Problem 10.11

16. © Copyright Pearson Prentice Hall Slide 16 of 40 Practice Problems

17. © Copyright Pearson Prentice Hall Percent Composition and Chemical Formulas > Slide 17 of 40 Molecular Formulas How does the molecular formula of a compound compare with the empirical formula? 10.3

18. © Copyright Pearson Prentice Hall Slide 18 of 40 Percent Composition and Chemical Formulas > Molecular Formulas The molecular formula of a compound is either the same as its experimentally determined empirical formula, or it is a simple whole-number multiple of its empirical formula. 10.3

19. Slide 19 of 40 © Copyright Pearson Prentice Hall Percent Composition and Chemical Formulas > Molecular Formulas 10.3 Methanal, ethanoic acid, and glucose all have the same empirical formula— CH 2 O.

20. Slide 20 of 40 © Copyright Pearson Prentice Hall Percent Composition and Chemical Formulas > Molecular Formulas 10.3

21. Slide 21 of 40 © Copyright Pearson Prentice Hall Percent Composition and Chemical Formulas > Steps to Determining the Molecular Formula of a Compound: 1.Determine the empirical formula 2.Find the molar mass of the empirical formula 3.Divide the molecular formula mass (given in problem) by the empirical formula mass (from step 2) 4.Multiply this integer by the empirical formula

22. © Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 22 of 40 10.12

23. © Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 23 of 40 Determine the molecular formula of a compound that contains 40.0 percent C, 6.71 percent H, and 53.29 percent O and has a molar mass of 60.05 g.

24. © Copyright Pearson Prentice Hall Slide 24 of 40 Practice Problems for Sample Problem 10.12

25. © Copyright Pearson Prentice Hall Slide 25 of 40 Section Quiz -or- Continue to: Launch: Assess students’ understanding of the concepts in Section 10.3 Section Quiz. 10.3.

26. © Copyright Pearson Prentice Hall Slide 26 of 40 1. Calculate the percent by mass of carbon in cadaverine, C 5 H 14 N 2, a compound present in rotting meat. a.67.4% C b.58.8% C c.51.7% C d.68.2% C 10.3 Section Quiz.

27. © Copyright Pearson Prentice Hall Slide 27 of 40 2. Which of the following is NOT an empirical formula? a.NO 2 b.H 2 N c.CH d.C 3 H 6 10.3 Section Quiz.

28. © Copyright Pearson Prentice Hall Slide 28 of 40 10.3 Section Quiz. 3. Determine the molecular formula of a compound that contains 40.0 percent C, 6.71 percent H, and 53.29 percent O and has a molar mass of 60.05 g. a.C 2 H 4 O 2 b.CH 2 O c.C 2 H 3 O d.C 2 H 4 O

29. © Copyright Pearson Prentice Hall Slide 29 of 40 Percent Composition and Chemical Formulas > Concept Map 10 Concept Map 10 Solve the Concept Map with the help of an interactive tutorial.

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