Homework+6+Solutions

Homework+6+Solutions - 10/5/09 Quiz 1 Solutions (out of 7...

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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 U = KE. For an isothermal process, ΔT = 0, meaning that ΔKE = 0 (since KE=3/2 k B T) and that ΔU = 0. Alternatively, ΔU = 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 ΔU = 0. 3. What thermodynamic parameter do you measure with a a) constant pressure calorimeter? (1 pt) ΔH b) constant volume calorimeter? (1 pt) ΔU
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BME 221 Fall 2009 - Quiz 2 (4 pts total) 1. Based only on osmotic pressure considerations, can a tree grow taller or shorter in warmer climates compared to cooler climates? Explain. Since trees achieve transport up the trunk to high branches by utilizing osmotic pressure, increased osmotic pressure provides adequate transport for a taller height. (Either a or b is fine as an explanation for why osmotic pressure increases) (2 pts) 2. . As temperature increases, the osmotic pressure increases as well. 3. Since osmotic pressure in an entropic effect, it is more pronounced at higher T. 2. Why are deviations from ideal behavior more of an issue in electrolyte solutions than non- electrolyte solutions? (2 pts) Electrolytes are charged, meaning there are additional electrostatic interactions (even at larger distances than VanderWaal interactions). This leads to a lower effective concentration of free ions because of the formation of ion pairs, etc.
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11/18/09 Quiz 3 (7 pts) 5. a) Formulate LeChatlier’s principle.  (1 pt) b) Name 3 variables you can make predictions about based on LeChatlier’s principle.  (1 pt  each) 6. Why is ΔG° so negative for ATP hydrolysis? Give at least 2 reasons.  (2 pts) 7. How does biochemistry accomplish reactions that are not by themselves spontaneous?  (1 pt) 1. a)  The system will shift to minimize the change that is applied. LeChatlier’s Principle gives  you a prediction about how a system at equilibrium will change based on changes to certain  variables. b) concentration/pH (same answer), temperature, (partial) pressure, volume 2. The hydrolysis of ATP into ADP and inorganic phosphate reduces steric crowding, creates  more resonance structures, and reduces electrostatic repulsion. 1.
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Homework+6+Solutions - 10/5/09 Quiz 1 Solutions (out of 7...

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