课程名称︰普通化学丙 课程性质︰必修 课程教师︰黄信炅 开课学院：工学院 开课系所︰工科海洋系 考试日期（年月日）︰100/6/23 考试时限（分钟）：150分钟左右 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : 1. Use the following data to estimate △Hf0 for potassium chloride(4%) K(s) + 1/2 Cl2(g) --> KCl(s) ----------------------------------- Lattice energy -690.kJ/mol First ionization energy of K 419kJ/mol Electron affinity of Cl -349kJ/mol Bond of energy of Cl2 239kJ/mol Enthalpy of sublimation of K 64kJ/mol 2. Write the most possible Lewis structure for each of the following: (10pts) (a) NO2 (b) NO (c) I3- (d) NO43- (e) SF6 3. Predict the Lewis structure and the molecular structure for each of the following.(6pts) (a) IF5 (b) XeF2 (c) CF2Cl2 4. Nitrous oxide (N2O) has three possible Lewis structure: . . .. .. :N=N=O: <--> :N≡N－O: <--> :N－N≡O: ' ' '' '' Given the following bond lengths, N－N 167pm N＝N 120pm N≡N 110pm N－O 147pm N＝O 115pm Rationalize the obaervation that the N－N bond length in N2O is 112 pm and that the N－O bond length is 119 pm. Can you eliminate any of the resonance structures? Please explain the reasons.(6pts) 5. The diatomic molecular OH exists in the gas phase. The bond length and bond energy have been measured to be 97.06 pm and 424.7 kJ/mol, respectively. Assume that the OH molecule is analogous to the HF molecule and that the MOs result from the overlap of a pz orbital from oxygen and the 1s orbital of hydrogen (the O-H bond lies along the z axis). (a) Draw pictures of the sigma bonding and antibonding molecular orbitals in OH.(2pts) (b) Which of the two MOs has the greater hydrogen 1s character?(2pts) (c) Can the 2px orbital of oxygen from MOs with the 1s orbital of hydrogen? (2pts) (d) Estimate the bond orders for OH and OH+.(4pts) 6. Consider the molecular-orbital energy-level diagrams for O2 and NO. Which of the following is true?(4pts) I. Both molecules are paramagnetic. II. The bond strength of O2 is greater than the bond strength of NO. III. NO is an example of a homonuclear diatomic molecule. IV. The ionization energy of NO is smaller than the ionization energy of NO+. (A) I only (B) I and II only (C) I and IV (D) II and III (E) I, II, and IV 7. Consider the following data for xenon: Triple point: -121℃, 280 torr Normal melting point: -112℃ Normal boiling point: -107℃ Which is more dense. Xe(s), or Xe(l)? How do the melting point and boiling point of xenon depend on pressure? Please estimate the heat of vaporization for xenon as possible as you can(Please explain the reasons)(6pts) 8. A metal crystallizes in a body-centered unit cell with an edge length of 2.00102pm. Assume the atoms in the cell touch along the cube diagonal. The percentage of empty volume in the unit cell will be:(4pts) (a) 0% (b) 26.0% (c) 32.0% (d) 68.0% (e) none of these 本题数字有误送分 9. At a given temperture, you have a mixture of benzene(vapor pressure of pure benzene = 745 torr) and toluene (vapor pressure of pure toluene = 290 torr). The mole fraction of benzene in the vapor above the solution is 0.590. Assuming ideal behavior, calculate the mole fraction of toluene in the solution.(4pts) (a) 0.213 (b) 0.778 (c) 0.641 (d) 0.359 (e) 0.590 10. The rate of the reaction O(g) + NO2(g) --> NO(g) + O2(g) was studied at a certain temperature. (a) In the first set of experiment NO2 was in large excess, at a concentration of 1.0 × 10^13 molecules/cm^3 with the following data collected. Time(s) │ [O](atoms/cm^3) ──────┼────────── 0 │ 5.0*10^9 1.0*10^-2 │ 1.9*10^9 2.0*10^-2 │ 6.8*10^8 3.0*10^-2 │ 2.5*10^8 ──────┴────────── What is the order of the reaction with respect to oxygen atoms?(4pts) (b) The reaction is known to be first order with respect to NO2. Determine the overall rate law and the value of the rate constant.(4pts) 11. Given this data from a study on how the rate of a reason was affected by the concentration of the reactants Experiment [A] [B] [C] Initial rate(mol L-1 hr-1) 1 0.200 0.100 0.600 5.0 2 0.200 0.400 0.400 80.0 3 0.600 0.100 0.200 15.0 4 0.200 0.100 0.200 5.0 5 0.200 0.200 0.400 20.0 Please determine the rate law and the rate constant for this reaction.(4pts) 12. Nitric oxide and bromide at initial partial pressures of 98.4 and 41.3 torr, respectively, were allowed to react at 300. K. At equilibrium the total pressure was 110.5 torr. The reaction is 2 NO(g) + Br2(g) <---> 2 NOBr(g) (a) Calculate the value of Kp(2pts) (b) What would be the partial pressures of all species if NO and Br2, both at an initial partial pressure of 1.0 atm, were allowed to come to equilibrium at this temperature? (2pts) 13. Hydrogen cyanide gas (HCN), a powerful respiratory inhibitor, is highly toxic. It is a very weak acid(Ka = 6.2 * 10^-10) when dissolved in water. If a 50.0-mL sample of 0.100M HCN is titrated with 0.100M NaOH, calculate the pH of the solution. (a) after 8.00mL of 0.100M NaOH has been added.(2pts) (b) at the halfway point of the titration.(2pts) (c) at the equivalence point of the titration.(2pts) 14. A solution is prepared by mixing 100.0mL of 1.0*10^-4M Be(NO3)2 and 100.0 mL of 8.0M NaF. Be2+(aq) + F-(aq) <--> BeF+(aq) K1 = 7.9*10^4 BeF+(aq) + F-(aq) <--> BeF2(aq) K2 = 5.8*10^3 BeF2(aq) + F-(aq) <--> BeF3-(aq) K3 = 6.2*10^2 BeF3-(aq)+ F-(aq) <--> BeF42-(aq) K4 = 2.7*10^1 Calculate the equilibrium concentration of F-, Be2+, BeF+, BeF2, BeF3-, and BeF42- inthis solution.(12pts) 15. The Ostwald process for the commercial production of nitric acid involves three steps: 4 NH3(g) + 5 O2(g) --> 4 NO(g) + 6 H2O(g) on Pt at 825℃ 2 NO(g) + O2(g) --> 2 NO2(g) 3 NO2(g) + H2O(l) --> 2 HNO3(l) + NO(g) (a) Calculate △H0, △S0, △G0, and K(at 298K) for each of three steps in the Ostwald process(12pts) (b) Calculate the equilibrium constant for the first step at 825℃, assuming △H0 and △S0 do not depend on temperature.(2pts) (c) Is there a thermodynamic reason for the high temperature in the first step, assuming standard conditions? (2pts) △Hf0(kJ/mol) △Gf0(kJ/mol) S0(J/Kmol) NH3(g) -46 -17 193 NH3(aq) -80 -27 111 NO(g) 90 87 211 NO2(g) 34 52 240 HNO3(aq) -207 -111 146 HNO3(l) -174 -81 156 H2O(l) -286 -237 70 H20(g) -242 -229 189 O2(g) 0 0 205 16. Prove that a gaseous reaction, △G = △G0 + RT In Q Π(P products)^np where Q is the reaction quotient, Q = ──────────.(6pts) Π(P reactants)^nr --

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