Chem271_F09_x2_key

Chem271_F09_x2_key - Chemistry 271, Section 22xx Prof....

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Chemistry 271, Section 22xx Your Name: Prof. Jason Kahn University of Maryland, College Park Your SID #: General Chemistry and Energetics Exam II (100 points total) Your Section #: November 4, 2009 You have 53 minutes for this exam. Exams written in pencil or erasable ink will not be re-graded under any circumstances. Explanations should be concise and clear . I have given you more space than you should need. There is extra space on the last page if you need it. You will need a calculator for this exam. No other study aids or materials are permitted. Generous partial credit will be given, i.e. , if you don’t know, guess. Useful Equations: K a = [H + ][A ]/[HA] pH = – log([H + ]) K b = [HA][HO ]/[A ] K w = [H + ][HO ] pH = pK a + log [A ]/[HA] G = – n ℱ∆ E R = 0.08206 L·atm/mole K 0 °C = 273.15 K ln K eq = – H°/(RT) + S°/R S q / T 0 pH = – log([H + ]) PV = n R T S = k ln W G = H T S R = 8.314 J/mole K = 96500 C(oulomb)/mole 1 V = 1 J/C G ° = – RT ln K eq W = N!/( n i !) n i / n 0 = exp[–( E i - E 0 )/ kT ] T M = H°/[ S°+ R ln( C T /4)] 2.303RT/ = 0.0592 Volts at 25 °C E = E° – 2.303(RT/ n )log 10 Q Chemical standard state: 1 M solutes, pure liquids, 1 atm gases Biochemical standard state: pH 7, all species in the ionic form found at pH 7 Honor Pledge: At the end of the examination time , please write out the following sentence and sign it, or talk to me about it: “I pledge on my honor that I have not given or received any unauthorized assistance on this examination.” (3 pts extra credit for filling out this page accurately and completely)
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Chemistry 271, Sections 22xx Exam II, 11/4/09 2/7 Score for the page 1. (20 pts) Multiple choice: Circle the single best answer for each question (a; 4 pts) The Boltzmann distribution refers to the distribution of (a) microstates over configurations. (b) particles within boxes. (c) energy among particles. (d) entropy among reactants. (e) None of the above. (b; 4 pts) Free energy is useful because it (a) tells us the amount of heat released by a reaction. (b) is maximized when reactions come to equilibrium. (c) is constant during isothermal expansion of a gas. (d) reduces the fundamental spontaneity condition S universe > 0 to state functions solely of the system. (e) All of the above. (c; 4 pts) Entropy is given as a logarithm of the number of microstates because (a) it must be an increasing and extensive function of W. ln(W 1 W 2 ) = lnW 1 + ln W 2 (b) the number of microstates cannot be calculated.
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Chem271_F09_x2_key - Chemistry 271, Section 22xx Prof....

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