课程名称︰普通化学乙下 课程性质︰系定必修 课程教师︰林金全 开课学院： 开课系所︰材料系 考试日期（年月日）︰2008年4月29日 考试时限（分钟）：160分钟 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : 1. Values of measured bond energies may vary greatly depending on the molecule studies. Consider the following reactions: (8%) NCl3(g) -> NCl2(g) + Cl(g) ΔH=375KJ/mol ONCl(g) -> NO(g) + Cl(g) ΔH=158KJ/mol Rationalize the difference in the values of ΔH for these reactions, even though each reaction appears to only involve the breaking of one N-Cl bond. 2. (1)If the force constant of NO is 1550 Nm^-2, determine the wave number of a line in the infrared spectrum of NO. The atomic mass of N is 14.003 amu, and the atomic mass fo O is 15.995 amu. (5%) (2)The microwave spectrum of CO shows that the transition from J=0 to J=1 requires electromagnetic radiation with a wavelength of 2.60 x 10^-3 m. a. Calculate the bond length of CO. See (1) for the atomic mass of O.(5%) b. Calculate the frequency of radiation absorbed in a rotational transition from the second to the third excited states of CO. (5%) 3. (1) Draw the MO energy-level diagram for each of the following species.(8%) (2) In terms of the molecular orbital model, which species in each of the following two pairs will most likely be the one to gain an electron? Explain.(8%) CN or NO O2^2+ of N2^2+ 4. A promising new material with great potential as fuel in solid rocket motors is ammonium dinitramide, NH4N(NO2)2. (12%) a. Draw Lewis structures (including resonance forms) for the dinitramide ion N(NO2)2^-. b. Ammonium dinitramide can decompose explosively to nitrogen, water, and oxygen. Write a balance equation for this reaction and use bond energies to estimate ΔH for the explosive decomposition of this compound. d. To estimate ΔH from bond energies, you made several assumptions. What are some of your assumptions ? 5. Predict the molecular structure and the bond angles for each of the following. (12%) a. XeCl2 b. ICl3 C. TeF4 d. PCl5 6. Acetic acid is responsible for the sour taste of vinegar. It can be manufactures using the following reaction: OH | CH3OH(g) + C≡H(g) -> CH3C＝O(l) Use tabulated values of bond energies to estimate ΔH for this reaction. Compare this result to the ΔH value calculated using standard enthalpies of formation. Explain any discrepancies.(12%) 7. The treatment of a particle in a one-dimensional box can be extended to a rectangular box of dimensions Lx, Ly, and Lz, yielding the following expression for energy: h^2 nx^2 ny^2 nz^2 E = -----(------ + ------ + ------) 8m Lx^2 Ly^2 Lz^2 The three quantum numbers nx, ny, and nz independently can assume only integer values. a. Determine the energies of the three lowest levels, assuming that the box is cubic.(5%) b. Describe the degeneracies of all the levels that correspond to quantum numbers having values of 1 or 2. How will these degeneracies change in a box where Lx≠Ly≠Lz? (5%) 8. (1) The wave function for 2Pz orbital in the hydrogen atom is 1 Z Ψ2Pz = --------(---)^3/2σe^-σ/2 cosθ 4√(2π) a0 where a0 is the value for the radius of the first Bohr orbit in meters (5.29x10^-11), σ is Z(r/a0), r is the value for the distance from the nucleus in meters, and θ is an angle. Calculate the value of Ψ2Pz at r=a0 for θ=0 (z axis) and for θ=90º (xy plane).(8%) (2) For hydrogen atoms, the wave function for the state n=3, l=0, ml=0 is 1 1 Ψ300 = ---------(---)^3/2 (27-18σ+2σ^2)e^-σ/3 91√(3π) a0 where σ=r/a0 and a0 is the Bohr radius (5.29x10^-11). Calculate the position of the nodes for this wave function.(8%) Information: (1)Bond energies C≡O = 1072KJ/mol C＝O = 745 KJ/mol C－O = 358 KJ/mol C－C = 347 KJ/mol N－H = 391 KJ/mol N－N = 160 KJ/mol N＝N = 418 KJ/mol N≡N = 947 KJ/mol H－O = 467 KJ/mol O＝O = 495 KJ/mol N－O = 201 KJ/mol N＝O = 607 KJ/mol C－H = 413 KJ/mol ∴ (2)Standard enthalpies of formation CH3OH(g) = -201 KJ/mol CO(g) = -110.5 KJ/mol Ch3COOH(l) -484 KJ/mol

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