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Quiz5B

# Quiz5B - like PE or KE translational or etc modes/atom for...

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Quiz 5B DL SEC _ _ Grade: 05/17/10 Last 6 digits of student ID _ _ _ _ _ _ Last name, first name: ________________ ________________ First three letters of your last name _ _ _ Useful formulae: Δ U TOT = Q + W; Δ U TOT = Δ E th + Δ E bond + Δ E nuclear + ...; W = P dV ; c vm = ½ k b N A #modes/molecule ; C v = c vm #moles ; PV = nRT (ideal gas); k b N A = R = 8.31 J/(K mol) 1. (55%) Marta has two containers with a fixed piston, so that the volume is also fixed. The two containers are both separately thermally insulated. In one box there is solid gold (Au), in the other there is Oxygen, a diatomic gas (O 2 ). The containers are both at room temperature (hint: room temperature is considered a low temperature, when it comes to the activation of vibrational modes in gases). a) List how many modes per atom you have for O 2 and for Au (specifying also which kind of modes they are,
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Unformatted text preview: like PE or KE, translational or. .. etc.). modes/atom for O 2 modes/atom for Au b) If Marta has the same setup with the same substances, but at 1000 K, considered a high temperature for activating modes, how will your answer to part a) change? Explain. 2. (30%) (Now suppose Marta uses the same setup room temperature for Question 1, but substitutes neon (Ne), a monatomic gas, for the nitrogen, so that the number of modes per atom in the gas changes from that of part 1 a). If Marta has 3 moles of Ne and 2 moles of Au, determine which of the two is easier to heat up to 1000 K (Hint: First determine how many modes per atom for each substance.) Show your work. 3. (15%) Marta’s friend, Rick, states that in general it's easier (takes less energy) to increase the temperature of O 2 gas than Ne gas. Do you agree? Explain....
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