Quiz+1+Solutions (1)

Quiz+1+Solutions (1) - U = KE. For an isothermal process, T...

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10/5/09 Quiz 1 Solutions (out of 7 points) 1. a) Write in words the first law of thermodynamics. (1 pt) The internal energy of an isolated system is constant. OR Energy can neither be created nor destroyed. b) For what system (open, closed, isolated) is it applicable? (1 pt) Isolated system; or, more generally, all systems c) Write the first law in mathematical form. (1 pt) ΔU = 0 for an isolated system or ΔU = q + w 2. a) For the expansion of an ideal gas, why is ΔU=0 for an isothermal process? (2 pts) An ideal gas has no potential energy, only kinetic energy. In other words, internal energy
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Unformatted text preview: U = KE. For an isothermal process, T = 0, meaning that KE = 0 (since KE=3/2 k B T) and that U = 0. Alternatively, U = q + w. Since the process is isothermal, as the system does work on the surroundings, it gains an equal amount of energy in the form of heat from the surroundings. q = -w and U = 0. 3. What thermodynamic parameter do you measure with a a) constant pressure calorimeter? (1 pt) H b) constant volume calorimeter? (1 pt) U...
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