Slide 1 of 40 chemistry

Slide 2 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

Slide 3 of 40 © Copyright Pearson Prentice Hall Percent Composition and Chemical Formulas > The Percent Composition of a Compound Percent Composition from Mass Data The relative amounts of the elements in a compound are expressed as the percent composition or the percent by mass of each element in the compound. 10.3

© Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 4 of

© Copyright Pearson Prentice Hall Slide 5 of 40 Practice Problems for Sample Problem 10.9 Problem Solving Solve Problem 33 with the help of an interactive guided tutorial.

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

© Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 7 of

© Copyright Pearson Prentice Hall Slide 8 of 40 Practice Problems for Sample Problem Problem Solving Solve Problem 34 with the help of an interactive guided tutorial.

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

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

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. The empirical formula of a compound shows the smallest whole-number ratio of the atoms in the compound. 10.3

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

Slide 13 of 40 © Copyright Pearson Prentice Hall Percent Composition and Chemical Formulas > Empirical Formulas You can take percent composition and use it do determine the empirical formula of a compound as follows: Assume you have 100g of the compound. With 100 g, you can change the percents to masses Convert the masses to moles. Find the smallest number of moles. Divide each mole value by the smallest number of moles. The values of the ratios will give you the subscripts of the empirical formula Watch out for fractions 0.33 is 1/3 – multiply by 3.

© Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 14 of

© Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 15 of 40

© Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 16 of 40

© Copyright Pearson Prentice Hall Slide 17 of 40 Practice Problems for Sample Problem Problem-Solving Solve Problem 37 with the help of an interactive guided tutorial.

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© Copyright Pearson Prentice Hall Slide 20 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

Slide 21 of 40 © Copyright Pearson Prentice Hall Percent Composition and Chemical Formulas > Molecular Formulas When given the empirical formula and the molar mass, determine the molar mass for the empirical formula, then divide the molar masses the whole number answer is then multiplied by the empirical formula.

Slide 22 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.

Slide 23 of 40 © Copyright Pearson Prentice Hall Percent Composition and Chemical Formulas > Molecular Formulas 10.3

© Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 24 of

© Copyright Pearson Prentice Hall Slide 25 of 40 Practice Problems for Sample Problem Problem-Solving Solve Problem 38 with the help of an interactive guided tutorial.

© Copyright Pearson Prentice Hall Slide 26 of 40 Practice Problems

© Copyright Pearson Prentice Hall Slide 27 of 40 Section Quiz -or- Continue to: Launch: Assess students’ understanding of the concepts in Section 10.3 Section Quiz

© Copyright Pearson Prentice Hall Slide 28 of 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.

© Copyright Pearson Prentice Hall Slide 29 of Which of the following is NOT an empirical formula? a.NO 2 b.H 2 N c.CH d.C 3 H Section Quiz.

© Copyright Pearson Prentice Hall Slide 30 of Section Quiz. 3. Determine the molecular formula of a compound that contains 40.0 percent C, 6.71 percent H, and percent O and has a molar mass of g. a.C 2 H 4 O 2 b.CH 2 O c.C 2 H 3 O d.C 2 H 4 O

© Copyright Pearson Prentice Hall Slide 31 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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