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ENERGY CHANGES AND RATES OF REACTION 712= /18K 76+ Tube 19T 17C 17A 741c (6K) 6) PART A True or False 1) _Heat is the transfer of thermal energy 2) A sample of a substance that has a smaller mass with a higher temperature will never have more thermal energy than a sample of a substance with a larger mass and a lower temperature. 3) An exothermic change means the system absorbs energy causing the beaker to become hotter, The fusion reaction in the core of the sun is an example of an exothermic change in a closed system 5) A chemical change has a greater AH than a nuclear change. The molar heat of vaporization of acetic acid is 4.184/mol. The vaporization of 4.0 g of acetic acid (HC,H,O,) would require 280. 7) Freezing and evaporation are both endothermic but sublimation from a gas to a solid is exothermic. 8) When water at 50°C is mixed with water of an equal volume at 20°C, the mixture will be 45°C 9) When water at SO™C is mixed with a piece of metal of equal mass at 20°C, the mixture will be 45°C. 10) A state function is a property that means a variable must be in standard state (SATP) conditions 11) One assumption made in calorimetry is that only some of the heat lost/gained by the system is equal to the enthalpy change 12) A glacier has more thermal energy that a cup of boiling water. PART B Short Answer/Calculations 1. a) Use the bond energies given in the table below to calculate enthalpy changes for the equation given under the table. Reminder, you may want to draw their Lewis structures first. Average Bond Energies (kJmol) H-a 348 CO 35 H-H C C СС 236 31 km 567 391 201 HE N-H NO O- 0-0 F 29 CH C-C C-N C-O CE co 0-5 ES 614 809 ml 299 495 m 1072 ml 615 415 mol 9 891 mol Ovo 00 CEN NAN NEN C 146 155 mol 0-0 CO(g) + 2 COAB) + 3 H 0(g) → CHg) - 40/19) (3T) ) b) Communicate the enthalpy change you found for the reaction in (a) above by using the four methods described in this unit. (70)