Copyright © Houghton Mifflin Company. All Rights Reserved.1 Chemistry 6/e Steven S. Zumdahl and Susan A. Zumdahl Chapter 6: THERMOCHEMISTRY

Copyright © Houghton Mifflin Company. All Rights Reserved.2 Thermochemistry The Nature of Energy React 1 React 2 React 3 React 4 React 5 React 6 React 7 React 8 Enthalpy and CalorimetryEnthalpy and Calorimetry React 9 React 10 React 11 Hess’s Law and Standard Enthalpies of FormationHess’s Law and Standard Enthalpies of Formation React 12 Present Sources of EnergyPresent Sources of Energy

Copyright © Houghton Mifflin Company. All Rights Reserved.3 The Nature of Energy

Copyright © Houghton Mifflin Company. All Rights Reserved.4 Initial Position In the initial position, ball A has a higher potential energy than ball B.

Copyright © Houghton Mifflin Company. All Rights Reserved.5 Final Position After A has rolled down the hill, the potential energy lost by A has been converted to random motions of the components of the hill (frictional heading) and to the increase in the potential energy of B.

Copyright © Houghton Mifflin Company. All Rights Reserved.6 Thermite

Copyright © Houghton Mifflin Company. All Rights Reserved.7 Ammonium Chloride and Barium Hydroxide

Copyright © Houghton Mifflin Company. All Rights Reserved.8 You strike an unlit match and it burns. Explain the energy transfers of this scenario using the terms exothermic, endothermic, system, surroundings, potential energy, and kinetic energy in your discussion. Sketch an energy level diagram for the process. React 1

Copyright © Houghton Mifflin Company. All Rights Reserved.9 Is the freezing of water an exothermic or an endothermic process? Explain. React 2

Copyright © Houghton Mifflin Company. All Rights Reserved.10 Classify each of the following processes as exothermic or endothermic. Explain. I.Your hand gets cold when you touch ice. II.The ice gets warmer when you touch it. III.Water boils in a kettle being heated on a stove. IV.Water vapor condenses on a cold pipe. V.Ice cream melts. React 3

Copyright © Houghton Mifflin Company. All Rights Reserved.11 For each of the following, define a system and its surroundings and give the direction of energy transfer. I.Methane is burning in a Bunsen burner in a laboratory. II.Water drops, sitting on your skin after you’ve been swimming, evaporate. III.Two chemicals mixing in a beaker give off heat. React 4

Copyright © Houghton Mifflin Company. All Rights Reserved.12 Hydrogen gas and oxygen gas react violently to form water. Which is lower in energy: a mixture of hydrogen and oxygen gases or water? Explain. Sketch an energy-level diagram for this reaction. React 5

Copyright © Houghton Mifflin Company. All Rights Reserved.13 Gas A 2 reacts with gas B 2 to form gas AB. The bond energy of AB is much greater than the bond energy of A 2 or B 2. Is the reaction for the formation of AB endothermic or exothermic? Explain. Which is or are lower in energy, the product or the reactants? React 6

Copyright © Houghton Mifflin Company. All Rights Reserved.14 Work vs. Energy Flow

Copyright © Houghton Mifflin Company. All Rights Reserved.15 Which of the following performs more work? A gas expanding against a pressure of 2 atm from 1.0 L to 4.0 L A gas expanding against a pressure of 3 atm from 1.0 L to 3.0 L React 7

Copyright © Houghton Mifflin Company. All Rights Reserved.16 Determine the sign of  E for each of the following with the listed conditions: An endothermic process that performs work. |work| > |heat| |work| < |heat| Work is done on a gas and the process is exothermic. |work| > |heat| |work| < |heat| React 8

Copyright © Houghton Mifflin Company. All Rights Reserved.17 Enthalpy and Calorimetry

Copyright © Houghton Mifflin Company. All Rights Reserved.18 A Coffee-Cup Calorimeter Made of Two Styrofoam Cups

Copyright © Houghton Mifflin Company. All Rights Reserved.19 A g sample of water at 90°C is added to a g sample of water at 10°C. a) The final temperature of the water should be: i) Between 50°C and 90°C. ii) 50°C iii) Between 10°C and 50°C. b) Calculate the final temperature of the water. React 9

Copyright © Houghton Mifflin Company. All Rights Reserved.20 A g sample of water at 90°C is added to a g sample of water at 10°C. a) The final temperature of the water is: i) Between 50°C and 90°C. ii) 50°C iii) Between 10°C and 50°C. b) Calculate the final temperature of the water. React 10

Copyright © Houghton Mifflin Company. All Rights Reserved.21 You have a Styrofoam cup with 50.0 g of water at 10  C. You add a 50.0-g iron ball at 90  C to the water. a) The final temperature of the water is: i) Between 50°C and 90°C. ii) 50°C iii) Between 10°C and 50°C. b) Calculate the final temperature of the water. React 11

Copyright © Houghton Mifflin Company. All Rights Reserved.22 Hess’s Law and Standard Enthalpies of Formation

Copyright © Houghton Mifflin Company. All Rights Reserved.23 The Principle of Hess’s Law

Copyright © Houghton Mifflin Company. All Rights Reserved.24 A Schematic Diagram of the Energy Changes for the Reaction CH 4 (g) + 2O 2 (g)  CO 2 (g) + 2H 2 O(l )

Copyright © Houghton Mifflin Company. All Rights Reserved.25 Using the following data, calculate the standard heat of formation of the compound ICl(g) at 25°C, and show your work:  H° (kJ/mol) Cl 2 (g)  2Cl(g)242.3 I 2 (g)  2I(g)151.0 ICl(g)  I(g) + Cl(g)211.3 I 2 (s)  I 2 (g)62.8 React 12

Copyright © Houghton Mifflin Company. All Rights Reserved.26 Present Sources of Energy

Copyright © Houghton Mifflin Company. All Rights Reserved.27 Energy Sources Used in the United States

Copyright © Houghton Mifflin Company. All Rights Reserved.28 The Earth’s Atmosphere