Ch 5 - Introductory Chemistry, 3rd Edition Nivaldo Tro...

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Roy Kennedy Massachusetts Bay Community College Wellesley Hills, MA Introductory Chemistry , 3 rd Edition Nivaldo Tro Chapter 5 Molecules and Compounds 2009, Prentice Hall
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Tro's "Introductory Chemistry", Chapter 5 2 Molecules and Compounds Salt Sodium—shiny, reactive, poisonous. Chlorine—pale yellow gas, reactive, poisonous. Sodium chloride—table salt. Sugar Carbon—pencil or diamonds. Hydrogen—flammable gas. Oxygen—a gas in air. Combine to form white crystalline sugar.
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Tro's "Introductory Chemistry", Chapter 5 3 Law of Constant Composition All pure substances have constant composition. All samples of a pure substance contain the same elements in the same percentages (ratios). Mixtures have variable composition.
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Tro's "Introductory Chemistry", Chapter 5 4 Compounds Display Constant Composition If we decompose water by electrolysis, we find 16.0 grams of oxygen to every 2.00 grams of hydrogen. Water has a constant mass ratio of oxygen to hydrogen of 8.0. 0 . 8 g 2.0 g 0 . 16 hydrogen of mass oxygen of mass Ratio Mass = = =
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Example 5.1—Show that Two Samples of Carbon Dioxide Are Consistent with the Law of Constant Composition. Since both samples have the same proportion of elements, carbon dioxide shows constant composition. Compare: Solution: composition = mass O : mass C Solution Map: Relationships: Sample 1: 4.8 g O, 1.8 g C; Sample 2: 17.1 g O, 6.4 g C proportion O:C Given: Find: compound composition element masses 2.7 C g 1.8 O g 4.8 1 Sample = 2.7 C g 6.4 O g 17.1 2 Sample =
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Tro's "Introductory Chemistry", Chapter 5 6 Practice—Show that Hematite Has Constant Composition if a 10.0 g Sample Has 7.2 g Fe and the Rest Is Oxygen; and a Second Sample Has 18.1 g Fe and 6.91 g O.
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Example 5.1—Show that Two Samples of Hematite Are Consistent with the Law of Constant Composition. Since both samples have the same proportion of elements, hematite shows constant composition. Compare: Solution: composition = mass Fe : mass O Solution Map: Relationships: Sample 1: 7.2 g Fe, (10.0-7.2) = 2.8 g O; Sample 2: 18.1 g Fe, 6.91 g O proportion Fe:O Given: Find: compound composition element masses 2.6 O g 2.8 Fe g 7.2 1 Sample = 2.61 C g 6.91 O g 18.1 2 Sample =
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Tro's "Introductory Chemistry", Chapter 5 8 Why Do Compounds Show Constant Composition? The smallest piece of a compound is called a molecule . Every molecule of a compound has the same number and type of atoms. Since all the molecules of a compound are identical, every sample will have the same ratio of the elements. Since all molecules of a compound are identical, every sample of the compound will have the same properties.
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Tro's "Introductory Chemistry", Chapter 5 9 Formulas Describe Compounds A compound is a distinct substance that is composed of atoms of two or more elements. Describe the compound by describing the number and type of each atom in the simplest unit of the compound.
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This note was uploaded on 08/06/2011 for the course CHEM 151 taught by Professor Mcbroom during the Summer '10 term at College of the Canyons.

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Ch 5 - Introductory Chemistry, 3rd Edition Nivaldo Tro...

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