Chemistry 17.2 1 of 33
17.2 Measuring and Expressing Enthalpy Changes 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. 2 of 33
17.2 Measuring and Expressing Enthalpy Changes > Calorimetry Calorimetry What basic concepts apply to calorimetry? 3 of 33
17.2 Measuring and Expressing > Enthalpy Changes Calorimetry Calorimetry is the precise measurement of the heat flow into or out of a system for chemical and physical processes. 4 of 33
17.2 Measuring and Expressing > Enthalpy Changes 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. 5 of 33
17.2 Measuring and Expressing > Enthalpy Changes Calorimetry The insulated device used to measure the absorption or release of heat in chemical or physical processes is called a calorimeter. 6 of 33
17.2 Measuring and Expressing > Enthalpy Changes 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. 7 of 33
17.2 Measuring and Expressing > Enthalpy Changes Calorimetry Constant-Volume Calorimeters Calorimetry experiments can be performed at a constant volume using a bomb calorimeter. 8 of 33
SAMPLE PROBLEM 17.2 9 of 33
SAMPLE PROBLEM 17.2 10 of 33
SAMPLE PROBLEM 17.2 11 of 33
SAMPLE PROBLEM 17.2 12 of 33
Practice Problems for Sample Problem 17.2 Problem Solving 17.13 Solve Problem 13 with the help of an interactive guided tutorial. 13 of 33
17.2 Measuring and Expressing Enthalpy Changes > Thermochemical Equations Thermochemical Equations How can you express the enthalpy change for a reaction in a chemical equation? 14 of 33
17.2 Measuring and Expressing Enthalpy Changes > Thermochemical Equations In a chemical equation, the enthalpy change for the reaction can be written as either a reactant or a product. 15 of 33
17.2 Measuring and Expressing > Enthalpy Changes Thermochemical Equations A chemical equation that includes the enthalpy change is called a thermochemical equation. 16 of 33
17.2 Measuring and Expressing > Enthalpy Changes Thermochemical Equations The heat of reaction is the enthalpy change for the chemical equation exactly as it is written. 17 of 33
17.2 Measuring and Expressing > Enthalpy Changes Exothermic Reaction Thermochemical Equations 18 of 33
17.2 Measuring and Expressing > Enthalpy Changes Endothermic Reaction Thermochemical Equations 19 of 33
Measuring and Expressing Enthalpy Changes > Thermochemical Equations Simulation 22 Simulate a combustion reaction and compare the H results for several compounds. 20 of 33
SAMPLE PROBLEM 17.3 21 of 33
SAMPLE PROBLEM 17.3 22 of 33
SAMPLE PROBLEM 17.3 23 of 33
SAMPLE PROBLEM 17.3 24 of 33
Practice Problems for Sample Problem 17.3 Problem Solving 17.15 Solve Problem 15 with the help of an interactive guided tutorial. 25 of 33
17.2 Measuring and Expressing > Enthalpy Changes Thermochemical Equations 26 of 33
17.2 Measuring and Expressing > Enthalpy Changes Thermochemical Equations The heat of combustion is the heat of reaction for the complete burning of one mole of a substance. 27 of 33
17.2 Section Quiz. Assess students understanding of the concepts in Section 17.2. Continue to: Section Quiz -or- Launch: 28 of 33
17.2 Section Quiz. 1. The change in temperature recorded by the thermometer in a calorimeter is a measurement of a. the enthalpy change of the reaction in the calorimeter. b. the specific heat of each compound in a calorimeter. c. the physical states of the reactants in a colorimeter. d. the heat of combustion for one substance in a calorimeter. 29 of 33
17.2 Section Quiz. 2. For the reaction CaO(s) + H 2 O(l) Ca(OH) 2 (s), H = 65.2 kj. This means that 62.5 kj of heat is during the process. a. absorbed b. destroyed c. changed to mass d. released 30 of 33
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. a. 2.00 kj b. 3.60 kj c. 36.0 kj d. 360 kj 31 of 33
17.2 Section Quiz. 4. Which of the following is a thermochemical equation for an endothermic reaction? a. CH 4 (g) + 2O 2 (g) CO 2 (g) + 2H 2 O(g) + 890 kj b. 241.8 kj + 2H 2 O(l) 2H 2 (g) + O 2 (g) c. CaO(s) + H 2 O(l) Ca(OH) 2 (s) 65.2 kj d. 2NaHCO 3 (s) 129 kj Na 2 CO 3 (s) + H 2 O(g) + CO 2 (g) 32 of 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? C 6 H 12 O 6 (s) + 6O 2 (g) 6CO 2 (g) + 6H 2 O(g) + 2808 kj/mol a. 4.66 kj b. 9.31 kj c. 1048 kj d. 6290 kj 33 of 33
END OF SHOW