试题 : 课程名称︰普通化学乙下 课程性质︰系内必带 课程教师︰金必耀 开课学院：工学院 开课系所︰土木工程学系 考试日期（年月日）︰99/4/23 考试时限（分钟）：120min 是否需发放奖励金：是，谢谢 （如未明确表示，则不予发放） 试题 : 1.(8%) A balloon is inflated to its full extent by heating the air inside it. In the final stages of this process the volume of the balloon changes from 4.00×10^6 L to 4.50×10^6 L by addition of 1.3×10^8 J of energy as heat. Assuming the balloon expands against a constant pressure of 1.0 atm, calculate ΔE for the process. 2.(8%) When 2.00 mol of SO2(g) react completely with 1.00 mol of O2(g) to from 2.00 mol of SO3(g) at 25℃ and a constant pressure of 1.00 atm, 198 kJ of energy are released as heat. Calculate ΔE & ΔH for the process. 3.(8%) It takes 78.2 J to raise the temperature of 45.6 g of lead by 13.3℃. What is the specific heat capacity of lead ? What is the molar heat capacity of lead? 4.(8%) The standard enthalpy for formation of H2O(l) at 298K is -285.6 kJ/mol. Calculate the change in internal energy for the following process at 298K and 1 atm: H2O(l) --> H2(g) + 1/2O2(g) ΔE°=? 5.(8%) The heat required to raise the temperature form 300.0K to 400.0K for 1 mol of gas at constant volume is 2079 J. The internal energy required to heat the same gas at constant pressure form 550.0K to 600.0K is 1305 J. The gas does 150.0 J work during this expansion at constant pressure. Is this gas behaving ideally? Is the gas a monoatomic gas? Explain. 6.(8%) Consider the reaction: 2SO2(g) + O2(g) --> 2SO3(g) carried out at 25℃ at 1 atm. Using the given data, Calculate the ΔS°,ΔH°,and ΔG°. | | S°(J/mol-K) | H°(f) (kJ/mol) | | SO2(g) | 248 | -297 | | O2(g) | 205 | 0 | | SO3(g) | 257 | -396 | 7.(8%) Compare the entropy of the following process and predict the sign of the sign of the entropy change. (a) Solid CO2 to gaseous CO2 (b) Gaseous nitrogen from 1 atm to 0.01 atm (c) Solid sugar is added to water to form solution. (d) lodine vapor condense on a cold surface 8.(8%) At what temperatures is the following process spontaneous at 1 atm? Br2(l) --> Br2(g), where ΔH°=31.0 kJ/mol and ΔS°=39.0 J/mol-K. What is the normal boiling point? 9.(8%) The diffusion rate of an unknown gas is measured and found to be 31.50 mL/min. Under identical experimental conditions the diffusion rate of O2 is found to be 30.50 mL/min. Which of the following is unknown gas: CH4, CO, NO, CO2, NO2? 10.(8%) Consider the isothermal expansion of the 1.00mol of ideal gas at 27℃. The volume increases from 30.0L to 40.0L. Calculate q, w, ΔE, ΔH, ΔS, and ΔG for two situation: (a) a free expansion (b) a reversible expansion 11.(8%) A chemist in the land of Narnia has successfully synthesized a new family of compounds called Rubikan as shown in the following figure: These compounds are made up of many cubelets, which can rotate around different symmetry axes freely without breaking up. This leads to an enormous amount of conformations for this kind of molecules. Based on the discrete mathematics, there are 4.33×10^19 possibilities for 3×3×3 Rubikan. Suppose each conformation has equal probability to occur even at 0K . Calculate the residual entropy for a mole of compounds 3×3×3 Rubikan using the Boltzmann formula. Compare your result with the molar residual entropy of carbon monoxide.(Boltzmann constant kB=1.38×10^-23 J/K) 12.(8%) In 1858, J. Waterston found a clever way to estimate molecular size from macroscopic properties of a liquid, by comparing its surface tension and heat of vaporization. =========================================================================== The surface tension of water, Σ, is the work per unit area needed to create more free energy. The heat of vaporization of water, ΔHvap, is the energy per unit volume we must ass to liquid water (just below its boiling point) to convert it completely to gas (just above its boiling point). Picture a liquid as a cubic array with N molecules per centimeter in each of three directions. Each molecules has weak attractive force to its six nearest neighbors. Suppose it takes energy εto break one of these bonds. Then the complete vaporization of 1 cm^3 of liquid requires that we break all the bounds. The corresponding energy is ΔHvap *(1cm^3). Next consider a molecule on the surface of the fluid. It has only five bonds -- the nearest neighbor on the top is missing (suppose this is a fluid-vacuum interface). Draw a picture to help you visualize this situation . Thus, create more surface area requires that we break bonds. The energy needed to do that, divided by the new area created, is Σ. =========================================================================== (a) For water, ΔHvap=2.3×10^9 Jm^-3 and Σ=0.072 Jm^-2. Estimate N, ε. (b) Assuming the molecules are closely packed, estimate the approximate molecular diameter. (c) What eatimate for Avogadro's number do you get? 13.(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 1 N 8RT Z(A)= --- --- √(-----) A 4 V πM (b) the number of collisions per second for a single gas particle with diameter d N 8πRT Z(A)= √(2) --- d^2 √(-------) V M In each of these two questions, you also need to explain the origin of the numerical prefactor qualitatively. --

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