課程名稱︰普通化學甲下 課程性質︰外系生/高中生 課程教師︰金必耀 開課學院：理學院 開課系所︰化學系 考試日期（年月日）︰98/4/24 考試時限（分鐘）：150分鐘 是否需發放獎勵金：是 （如未明確表示，則不予發放） 試題 : 1. You remember that ΔG0 is related to RTln(K), but can’t remember if it is RTln(K) or –RTln(K). Realizing whatΔG0 and K mean, how can you figure out correct sign? (8 %) 2. Consider the isothermal expansion of 1.00 mol of ideal gas at 27℃. The volume increases from 30.0 L to 40.0 L. Calculate q, w, ΔE, ΔH, ΔS, and Δ G for two situations: (12 %) a. a free expansion b. a reversible expansion 3. For the reaction at 298K, 2NO2(g) → N2O4(g), the value of ΔH0 and ΔS0 are -58.03 kJ and -176.6 J/K, respectively. (12 %) (a) What is the value of ΔG0 at 298K? (b) Assuming that ΔH0 and ΔS0 do not depend on temperature, at what temperature is ΔG0 = 0 (c) Is ΔG0 negative above or below this temperature? 4. Combine the equations ΔG0 = nFε0 and ΔG0 = ΔH0 - TΔS0, to derive an expansion for ε0 as a function of temperature. Describe how one can graphically determine ΔH0 and ΔS0 from measurement of ε0 at different temperatures. Assume that ΔH0 and ΔS0 do not depend on temperature. (10 %) 5. Calculate the percent dissociation of the acid in each of the following solutions. (12 %) (a) 0.50 M acetic acid (Ka = 1.8 x 10^-5) (b) 0.050 M acetic acid (c) 0.0050 M acetic acid (d) Use Le Chatelier's principle to explain why percent dissociation increases as the concentration of a weak acid drcreases. 6. Give a qualitative physical interpretation for (a) the collision rate of the gas particles with a section of wall that has an area A is Z = 1/4 x N/V x sqrt(8RT/πM) x A (b) the number of collisions per second for a single gas particle with a diameter d is Z = sqrt(2) x N/V x d^2 x sqrt(8πRT/M) x A In each of these two questions, you also need to explain the origin of the numerical prefactor qualitatively. (8 %) 7. What partial of O2 at 50℃ and 0.050 L is required to react stoichiometrically with the vapor from 0.025 mL gasoline (octane, C8H18, with a density of 0.74 g/mL) to yield CO2(g) and H2O(g)? Assuming that the O2 is at its normal partial pressure in air, what total pressure (air + fuel vapor) is present in the 0.050 L volume? (10 %) 8. What is the standard enthalpy change (298 K) in the Harver-Bosch process for the synthesis of ammonia, 3H2(g) + N2(g) → 2NH3(g)? Industrially, this reaction is generally run at 800 K. Use follow equation to develop a working formula for ΔHT0 for this reaction, and calculate ΔH8000. (The standard formation heat of ammonia at 298 K is -11.02 kcal/mol) (10 %) ΔHT20 = ΔHT10 + [Σvp x Cp(P) - Σvr x Cp(R)](T2 - T1) ============================================================= Substances Cp (cal/mol K) ============================================================= H2(g) 6.889 N2(g) 6.961(8.293 at 1500 K) NH3(g) 8.38 ============================================================= 9. Suppose the Jould experiment is run with two different gases, say He and Ar, in the left-hand and right-hand containers, of volumes of VHe and VAr, at the same pressure. When the stopcock is opened, the gases will mix and, after a brief fluctuation, the pressure of the system will return to the same value as before. Assuming the gases act independently, find a formula for ΔS. Show using Boyle's law and Dalton's law of partial pressures that your formula is equivalent to ΔS = -nR(XHe x ln(XHe) + XAr x ln(XAr)). Where n is total moles of gas and the X's are mole fractions. (This is known as the entropy of mixing, and is readily generalized to an arbitrary number of components.) What is the nature of the brief fluctuation above? (8 %) 10. Cu++ ion forms a complex Cu(NH3)4++ when ammonia is added to a 0.025 M CuSO4 solution. The formation constatnt for this complex is Kf = 1 x 10^12. What minimum concentration of ammonia at equilibrium is neesed to keep [Cu++] below 10^(-15) M? (10 %) 11. Listed below are "battery" reactions. Match each reaction with following appropriate letter. Each answer is used only once. (10 %) i. 2MnO2(s) + H2O(l) + 2e- → Mn2O3(s) + 2OH-(aq) ii. H2(aq) + 2OH-(aq) → 2H2O(l) + 2e- iii. 2PbSO4(s) + 2H2O(l) → Pb(s) + PbO2(s) + 4H+(aq) + 2SO4^(2-)(aq) iv. Zn(s) → Zn2+(aq) + 2e- v. 2MnO2(s) + 2NH4+(aq) + 2e- → Mn2O3(s) + 2NH3(aq) + H2O(l) (a) Leclanche dry cell cathode (b) alkaline dry cell cathode (c) Daniel cell cathode (d) Leclanche dry cell anode (e) Reverse of Plante's lead-acid battery overall reaction (f) a typical fuel cell cathode (g) Plante's lead-acid battery overall reaction (h) a typical fuel cell anode END --

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