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Chemistry 17.2

Chemistry 17.2. Measuring and Expressing Enthalpy Changes. 17.2.

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Chemistry 17.2

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  1. Chemistry 17.2

  2. Measuring and Expressing Enthalpy Changes 17.2 • A burning match releases heat to its surroundings in all directions. How much heat does this exothermic reaction release? You will learn to measure heat flow in chemical and physical processes by applying the concept of specific heat.

  3. 17.2 Calorimetry • Calorimetry • What basic concepts apply to calorimetry?

  4. 17.2 Calorimetry • Calorimetry is the precise measurement of the heat flow into or out of a system for chemical and physical processes.

  5. 17.2 Calorimetry • In calorimetry, the heat released by the system is equal to the heat absorbed by its surroundings. Conversely, the heat absorbed by a system is equal to the heat released by its surroundings.

  6. 17.2 Calorimetry • The insulated device used to measure the absorption or release of heat in chemical or physical processes is called a calorimeter.

  7. 17.2 Calorimetry • Constant-Pressure Calorimeters • The heat content of a system at constant pressure is the same as a property called the enthalpy (H) of the system.

  8. 17.2 Calorimetry • Constant-Volume Calorimeters • Calorimetry experiments can be performed at a constant volume using a bomb calorimeter.

  9. 17.2

  10. 17.2

  11. 17.2

  12. 17.2

  13. for Sample Problem 17.2 Problem Solving 17.13 Solve Problem 13 with the help of an interactive guided tutorial.

  14. 17.2 Thermochemical Equations • Thermochemical Equations • How can you express the enthalpy change for a reaction in a chemical equation?

  15. 17.2 Thermochemical Equations • In a chemical equation, the enthalpy change for the reaction can be written as either a reactant or a product.

  16. 17.2 Thermochemical Equations • A chemical equation that includes the enthalpy change is called a thermochemical equation.

  17. 17.2 Thermochemical Equations • The heat of reaction is the enthalpy change for the chemical equation exactly as it is written.

  18. 17.2 Thermochemical Equations Exothermic Reaction

  19. 17.2 Thermochemical Equations Endothermic Reaction

  20. Thermochemical Equations • Simulation 22 • Simulate a combustion reaction and compare the ∆H results for several compounds.

  21. 17.3

  22. 17.3

  23. 17.3

  24. 17.3

  25. for Sample Problem 17.3 Problem Solving 17.15 Solve Problem 15 with the help of an interactive guided tutorial.

  26. 17.2 Thermochemical Equations

  27. 17.2 Thermochemical Equations • The heat of combustion is the heat of reaction for the complete burning of one mole of a substance.

  28. 17.2 Section Quiz. • 17.2.

  29. 17.2 Section Quiz. • 1. The change in temperature recorded by the thermometer in a calorimeter is a measurement of • the enthalpy change of the reaction in the calorimeter. • the specific heat of each compound in a calorimeter. • the physical states of the reactants in a colorimeter. • the heat of combustion for one substance in a calorimeter.

  30. 17.2 Section Quiz. • 2. For the reaction CaO(s) + H2O(l) Ca(OH)2(s),  H = 65.2 kJ. This means that 62.5 kJ of heat is __________ during the process. • absorbed • destroyed • changed to mass • released

  31. 17.2 Section Quiz. • 3. How much heat is absorbed by 325 g of water if its temperature changes from 17.0°C to 43.5°C? The specific heat of water is 4.18 J/g°C. • 2.00 kJ • 3.60 kJ • 36.0 kJ • 360 kJ

  32. 17.2 Section Quiz. • 4. Which of the following is a thermochemical equation for an endothermic reaction? • CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) + 890 kJ • 241.8 kJ + 2H2O(l) 2H2(g) + O2(g) • CaO(s) + H2O(l)  Ca(OH)2(s) 65.2 kJ • 2NaHCO3(s) 129 kJ Na2CO3(s) + H2O(g) + CO2(g)

  33. 17.2 Section Quiz. • 5. Oxygen is necessary for releasing energy from glucose in organisms. How many kJ of heat are produced when 2.24 mol glucose reacts with an excess of oxygen? • C6H12O6(s) + 6O2(g)  6CO2(g) + 6H2O(g) + 2808 kJ/mol • 4.66 kJ • 9.31 kJ • 1048 kJ • 6290 kJ

  34. END OF SHOW

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