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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu How to Use This Presentation To View the presentation as a slideshow with effects select “View” on the menu bar and click on “Slide Show.” To advance through the presentation, click the right-arrow key or the space bar. From the resources slide, click on any resource to see a presentation for that resource. From the Chapter menu screen click on any lesson to go directly to that lesson’s presentation. You may exit the slide show at any time by pressing the Esc key.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Section 3 Using Chemical Formulas Lesson Starter The chemical formula for water is H 2 O. How many atoms of hydrogen and oxygen are there in one water molecule? How might you calculate the mass of a water molecule, given the atomic masses of hydrogen and oxygen? In this section, you will learn how to carry out these and other calculations for any compound.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Section 3 Using Chemical Formulas Objectives Calculate the formula mass or molar mass of any given compound. Use molar mass to convert between mass in grams and amount in moles of a chemical compound. Calculate the number of molecules, formula units, or ions in a given molar amount of a chemical compound. Calculate the percentage composition of a given chemical compound.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 A chemical formula indicates: the elements present in a compound the relative number of atoms or ions of each element present in a compound Chemical formulas also allow chemists to calculate a number of other characteristic values for a compound: formula mass molar mass percentage composition Section 3 Using Chemical Formulas

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Formula Masses The formula mass of any molecule, formula unit, or ion is the sum of the average atomic masses of all atoms represented in its formula. example:formula mass of water, H 2 O average atomic mass of H: 1.01 amu average atomic mass of O: 16.00 amu Section 3 Using Chemical Formulas average mass of H 2 O molecule: 18.02 amu

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Formula Masses The mass of a water molecule can be referred to as a molecular mass. The mass of one formula unit of an ionic compound, such as NaCl, is not a molecular mass. The mass of any unit represented by a chemical formula (H 2 O, NaCl) can be referred to as the formula mass. Section 3 Using Chemical Formulas

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Formula Masses, continued Sample Problem F Find the formula mass of potassium chlorate, KClO 3. Section 3 Using Chemical Formulas

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Formula Masses, continued Sample Problem F Solution The mass of a formula unit of KClO 3 is found by adding the masses of one K atom, one Cl atom, and three O atoms. Atomic masses can be found in the periodic table in the back of your book. In your calculations, round each atomic mass to two decimal places. Section 3 Using Chemical Formulas

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Formula Masses, continued Sample Problem F Solution, continued Chapter 7 Section 3 Using Chemical Formulas formula mass of KClO 3 = 122.55 amu

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Molar Masses The molar mass of a substance is equal to the mass in grams of one mole, or approximately 6.022  10 23 particles, of the substance. example: the molar mass of pure calcium, Ca, is 40.08 g/mol because one mole of calcium atoms has a mass of 40.08 g. The molar mass of a compound is calculated by adding the masses of the elements present in a mole of the molecules or formula units that make up the compound. Section 3 Using Chemical Formulas

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Molar Masses, continued One mole of water molecules contains exactly two moles of H atoms and one mole of O atoms. The molar mass of water is calculated as follows. Section 3 Using Chemical Formulas molar mass of H 2 O molecule: 18.02 g/mol A compound’s molar mass is numerically equal to its formula mass.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Molar Masses, continued Sample Problem G What is the molar mass of barium nitrate, Ba(NO 3 ) 2 ? Section 3 Using Chemical Formulas

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Molar Masses, continued Sample Problem G Solution One mole of barium nitrate, contains one mole of Ba, two moles of N (1  2), and six moles of O (3  2). Chapter 7 Section 3 Using Chemical Formulas molar mass of Ba(NO 3 ) 2 = 261.35 g/mol

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Molar Mass as a Conversion Factor The molar mass of a compound can be used as a conversion factor to relate an amount in moles to a mass in grams for a given substance. To convert moles to grams, multiply the amount in moles by the molar mass: Amount in moles  molar mass (g/mol) = mass in grams Section 3 Using Chemical Formulas

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Molar Mass as a Conversion Factor, continued Sample Problem H What is the mass in grams of 2.50 mol of oxygen gas? Section 3 Using Chemical Formulas

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Molar Mass as a Conversion Factor, continued Given: 2.50 mol O 2 Section 3 Using Chemical Formulas Sample Problem H Solution Unknown: mass of O 2 in grams Solution: moles O 2 grams O 2 amount of O 2 (mol)  molar mass of O 2 (g/mol) = mass of O 2 (g)

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Molar Mass as a Conversion Factor, continued Sample Problem H Solution, continued Calculate the molar mass of O 2. Section 3 Using Chemical Formulas Use the molar mass of O 2 to convert moles to mass.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Molar Mass as a Conversion Factor, continued Sample Problem I Ibuprofen, C 13 H 18 O 2, is the active ingredient in many nonprescription pain relievers. Its molar mass is 206.31 g/mol. a.If the tablets in a bottle contain a total of 33 g of ibuprofen, how many moles of ibuprofen are in the bottle? b.How many molecules of ibuprofen are in the bottle? c.What is the total mass in grams of carbon in 33 g of ibuprofen? Section 3 Using Chemical Formulas

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Molar Mass as a Conversion Factor, continued Sample Problem I Solution Section 3 Using Chemical Formulas Given:33 g of C 13 H 18 O 2 molar mass 206.31 g/mol Solution:a. grams moles Unknown:a. moles C 13 H 18 O 2 b. molecules C 13 H 18 O 2 c. total mass of C

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Molar Mass as a Conversion Factor, continued b. molesmolecules Section 3 Using Chemical Formulas c. moles C 13 H 18 O 2 moles C grams C Sample Problem I Solution, continued

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Molar Mass as a Conversion Factor, continued Section 3 Using Chemical Formulas a. c. b. Sample Problem I Solution, continued

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Standardized Test Preparation Multiple Choice 1.Which of the following compounds does not contain a polyatomic ion? A.sodium carbonate B.sodium sulfate C.sodium sulfite D.sodium sulfide

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Standardized Test Preparation Multiple Choice 1.Which of the following compounds does not contain a polyatomic ion? A.sodium carbonate B.sodium sulfate C.sodium sulfite D.sodium sulfide

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Standardized Test Preparation Multiple Choice 2.The correct formula for ammonium phosphate is A.(NH 4 ) 3 PO 4. B.(NH 4 ) 2 PO 4. C.NH 4 PO 4. D.NH 4 (PO 4 ) 2.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Standardized Test Preparation Multiple Choice 2.The correct formula for ammonium phosphate is A.(NH 4 ) 3 PO 4. B.(NH 4 ) 2 PO 4. C.NH 4 PO 4. D.NH 4 (PO 4 ) 2.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Standardized Test Preparation Multiple Choice 3.When writing the formula for a compound that contains a polyatomic ion, A.write the anion’s formula first. B.use superscripts to show the number of polyatomic ions present. C.use parentheses if the number of polyatomic ions is greater than 1. D.always place the polyatomic ion in parentheses.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Standardized Test Preparation Multiple Choice 3.When writing the formula for a compound that contains a polyatomic ion, A.write the anion’s formula first. B.use superscripts to show the number of polyatomic ions present. C.use parentheses if the number of polyatomic ions is greater than 1. D.always place the polyatomic ion in parentheses.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Standardized Test Preparation 4.The correct name for NH 4 CH 3 COO is A.ammonium carbonate. B.ammonium hydroxide. C.ammonium acetate. D.ammonium nitrate. Multiple Choice

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Standardized Test Preparation 4.The correct name for NH 4 CH 3 COO is A.ammonium carbonate. B.ammonium hydroxide. C.ammonium acetate. D.ammonium nitrate. Multiple Choice

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Standardized Test Preparation 5.Which of the following is the correct formula for iron(III) sulfate? A.Fe 3 SO 4 B.Fe 3 (SO 4 ) 2 C.Fe 2 (SO 4 ) 3 D.3FeSO 4 Multiple Choice

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Standardized Test Preparation 5.Which of the following is the correct formula for iron(III) sulfate? A.Fe 3 SO 4 B.Fe 3 (SO 4 ) 2 C.Fe 2 (SO 4 ) 3 D.3FeSO 4 Multiple Choice

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Standardized Test Preparation 6.The molecular formula for acetylene is C 2 H 2. The molecular formula for benzene is C 6 H 6. The empirical formula for both is A.CH. B.C 2 H 2. C.C 6 H 6. D.(CH) 2. Multiple Choice

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Standardized Test Preparation 6.The molecular formula for acetylene is C 2 H 2. The molecular formula for benzene is C 6 H 6. The empirical formula for both is A.CH. B.C 2 H 2. C.C 6 H 6. D.(CH) 2. Multiple Choice

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Standardized Test Preparation 12.What is an empirical formula, and how does it differ from a molecular formula? Answer: The empirical formula is the simplest whole- number ratio of the atoms in a chemical formula. The molecular formula is the actual number of atoms of each element in a chemical formula. The two formulas differ by an integer factor. Extended Response