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# Exam04answers pg5 - 018(part 2 of 2 5 points Is work done...

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1. pressure 2. entropy 3. free energy 4. temperature 5. heat correct Explanation: All except heat are independent of path and are dependent solely on the current state of the system. Heat (as well as work) is not a state function. It is dependent on the process or pathway. HOW you got there DOES affect the value of heat and work. 016 (part 1 of 1) 11 points Calculate the final temperature when 2.50 kJ of energy is transferred as heat to 1.50 mol N 2 at 298 K and 1 atm at constant pressure. 1. 82 C correct 2. 159 C 3. 92 C 4. 80 C 5. 75 C Explanation: 017 (part 1 of 2) 10 points Calculate the work for a system that releases 300 . 9 kJ of heat in a process for which the decrease in internal energy is 119 . 6 kJ. Correct answer: 181 . 3 kJ. Explanation: Δ U = - 119 . 6 kJ q = - 300 . 9 kJ To calculate this, we use the relationship Δ U = q + w, which arises from the first law of thermody- namics. Because the system releases heat, q will be a negative number as will Δ U , because it is a decrease in internal energy: w = Δ U - q = - 119 . 6 kJ - ( - 300 . 9 kJ) = 181 . 3 kJ . 018 (part 2 of 2) 5 points
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Unformatted text preview: 018 (part 2 of 2) 5 points Is work done on or by the system during this process? 1. on the system correct 2. by the system Explanation: Because work is positive, the surroundings will do work on the system. 019 (part 1 of 1) 10 points The enthalpy of combustion of benzoic acid (C 6 H 5 COOH) which is often used to calibrate calorimeters, is-3227 kJ / mol. When 1 . 392 g of benzoic acid was burned in a calorimeter, the temperature increased by 3 . 127 ◦ C. What is the heat capacity of the calorimeter? Correct answer: 11 . 763 kJ / ◦ C. Explanation: m = 1 . 392 g T = 3 . 127 ◦ C Δ H =-3227 kJ / mol MW C 6 H 5 COOH = 6(1 . 00794 g) + 7(12 . 0107 g) + 2(15 . 9994 g) = 122 . 121 g / mol C cal =-p m MW P (Δ H ) T =-± 1 . 392 g 122 . 121 g / mol ² (-3227 kJ / mol) 3 . 127 ◦ C = 11 . 763 kJ / ◦ C . 020 (part 1 of 1) 10 points The formation of chemical bonds from sepa-rated atoms...
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