10.3 Percent Composition and Chemical Formulas 1 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Chapter 10 Chemical Quantities 10.1 The Mole: A Measurement of Matter 10.2 Mole-Mass and Mole-Volume Relationships 10.3 Percent Composition and Chemical Formulas

2 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Do Now: 1.Calculate the percent composition of K 2 S. 2.How many grams of sulfur are in a 25 gram sample of K 2 S? 3.How many grams of potassium are in a 25 gram sample of K 2 S?

10.3 Percent Composition and Chemical Formulas 3 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Do Now: 1.Calculate the percent composition of K 2 S. K: 70.9%, S: 29.1% 2.How many grams of sulfur are in a 25 gram sample of K 2 S? 7.3 g 3.How many grams of potassium are in a 25 gram sample of K 2 S? 17.7 g

10.3 Percent Composition and Chemical Formulas 4 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Percent Composition from Mass Data Percent Composition of a Compound % by mass of element = mass of element mass of compound × 100%

10.3 Percent Composition and Chemical Formulas 5 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Percent Composition from the Chemical Formula Percent Composition of a Compound % by mass of element mass of element in 1 mol compound molar mass of compound × 100% =

10.3 Percent Composition and Chemical Formulas 6 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Calculate the mass of nitrogen and the mass of hydrogen in 125 g of NH 3 fertilizer. Sample Problem Calculating the Mass of an Element in a Compound Using Percent Composition

10.3 Percent Composition and Chemical Formulas 7 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. KNOWN mass of NH 3 = 125 g Sample Problem Analyze List the known and the unknowns. 1 UNKNOWNS mass of nitrogen = ? g N mass of hydrogen = ? g H

10.3 Percent Composition and Chemical Formulas 8 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. To calculate the mass of N, first write the conversion factor to convert from mass of NH 3 to mass of N g N 17.0 g NH 3 Sample Problem Calculate Solve for the unknowns. 2 Multiply the mass of NH 3 by the conversion factor g N 17.0 g NH g NH 3 ×= 103 g N

10.3 Percent Composition and Chemical Formulas 9 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. To calculate the mass of H, first write the conversion factor to convert from mass of NH 3 to mass of H. Sample Problem Calculate Solve for the unknowns. 2 Multiply the mass of NH 3 by the conversion factor. 3 g H 17 g NH g NH 3 ×= 22 g H 3 g H 17 g NH 3

10.3 Percent Composition and Chemical Formulas 10 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. The sum of the two masses equals 125 g, (103 g N + 22 g H = 125 g NH 3 ). Sample Problem Evaluate Does the result make sense? 3

10.3 Percent Composition and Chemical Formulas 11 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. empirical formula: lowest whole-number ratio of atoms or moles of elements in a compound. Empirical Formulas An empirical formula may or may not be the same as a molecular formula. CompoundMolecular Formula Empirical Formula Hydrogen PeroxideH2O2H2O2 HO WaterH2OH2OH2OH2O SucroseC 6 H 12 O 6 CH 2 O AcetyleneC2H2C2H2 CH

10.3 Percent Composition and Chemical Formulas 12 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Ethyne (C 2 H 2 ), also called acetylene, is a gas used in welders’ torches. These compounds have the same empirical formula (CH) but different molecular formulas. Styrene (C 8 H 8 ) is used in making polystyrene. Empirical Formulas

10.3 Percent Composition and Chemical Formulas 13 > Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. END OF 10.3