课程名称︰普通化学丙 课程性质︰必修 课程教师︰佘瑞琳 开课学院：理学院 开课系所︰化学系 考试日期（年月日）︰103/12/1 考试时限（分钟）：110分钟 试题 : General Chemistry (103-1 C) Midterm Exam-2 2014/12/01 C = 3.00 x 10^8 m/s; h = 6.626 x 10^-34 J-s; R_H = 1.096776 x 10^7 m^-1; 1 eV = - 1.6 x 10^-19 J Gas constant: R = 8.314 J/mol-K = 0.082 L-atm/mol-K; 1 L-atm = 101.3 J Ⅰ. Multiple choices questions (30%) 1. A system receives 435 J of heat from and delivers 421 J of work to its surroundings. Which one of the followings is true? (ΔU: internal energy) (a) q = +435 J (b) w = +421 J (c)ΔU = 856 J (d)ΔU = +14 J 2. Which transition in the hydrogen atom would emit light of a shorter wavelength? (a) n_i = 4 → n_f = 3 (b) n_i = 1 → n_f = 3 (c) n_i = 1 → n_f = 4 (d) n_i = 4 → n_f = 2 3. For the following types of electromagnetic radiation: x-ray, UV, visible, and IR, which of the following is correct? (a) highest energy: x-ray (b) longest wavelength: IR (c) highest frequency: UV (d) lowest energy: visible 4. Which of the following set of quantum numbers is the allowed combination? (a) (2, 2, -1) (b) (4, 3, -1) (c) (3, 1, -0) (d) (5, 2, +3) 5. Which of the following orbital diagram is correct for the ground-state electron configurations? http://ppt.cc/2UCp 6. How many orbitals have the quantum values of n 4 and 3? (a) 5 (b) 7 (c) 9 (d) 16 7. What is the valence shell electron configurations of the alkaline earth metals? (a) ns^1 (b) ns^2 (c) ns^2np^1 (d) ns^2np^5 (n ≧ 2) 8. According to the critical point, which of the following substances cannot be liquefied at 25 ℃? (a) NH3: 132 ℃ and 111 atm (b) N2: -147 ℃ and 34 atm (c) CO2: 31 ℃ and 72.8 atm (d) cannot determine from critical point. 9. Niobium oxide crystallizes in the following cubic unit cell. (a) 3 niobium atoms per unit cell. (b) 3 oxygen atoms per unit cell. (c) The empirical formula of niobium oxide is NiO2. (d) This is a covalent network solid. http://ppt.cc/bkcN 10.Choose the correct ranking of the following. 3- 2- - (a) increasing radius: N < O < F (b) increasing first ionization energy: N < O < F (c) metallic property: Be < Mg < Ca (d) increasing energy gap: Ca < As < I2 11.Using the following information, calculate the lattice energy of AgF(s). enthalpy of formation of AgF(s) -205 kJ/mol enthalpy of formation of Ag(g) +284 kJ/mol ionization energy of Ag(g) +731 kJ/mol enthalpy of formation of F(g) +79 kJ/mol electron affinity of F(g) +328 kJ/mol (a) 971 kJ/mol (b) 1050 kJ/mol (c) 1217 kJ/mol (d) 1627 kJ/mol 12.Which of the following substance has dipole-dipole interaction between molecules? (a) XeF2 (b) H2S (c) SO3 (d) ClF3 13.Which of the following is molecular solid? (a) SiO2(s) (b) C (graphite) (c) dry ice (CO2) (d) P4(s) 14.Which of the following ranking is correct? (a) Solubility in n-hexane: NaCH3COO < I2 (b) Solubility in water: C6H13OH < CH3OH (c) Solubility in water: O2(g) (35 ℃) < O2(g) (10 ℃) (d) Solubility in water: CO2(g) (1 atm) < CO2(g) (4 atm) 15.Which of the following ranking is correct? (a) Osmotic pressure: 0.10 m fructose = 0.10 m CH3COOH < 0.10 m NaNO3 (b) Surface tension: C2H5OH < CH2OHCH2OH < CH2OHCHOHCH2OH (c) Enthalpy of vaporization: C2H5OC2H5 < H2O (d) Normal boiling point: C2H5OH < CH3COCH3 Ⅱ. Problems (70%) 1. Write a balanced formation equation at standard conditions for each of the following compounds: (a) NaHCO3(s); (b) CICl3(l). (6.51, 4%) 2. Limestone stalactites and stalagmites are formed in caves by the following reaction: 2+ - Ca(aq) + 2HCO3(aq) → CaCO3(s) + CO2(g) + H2O(l) If 1 mol of CaCO3 forms at 298 K under 1 atm pressure, (a) what is the P-V work (in kJ) performs by the reaction when pushing back the atmosphere as the gaseous CO2 forms. At the same time, 38.95 kJ of heat is absorbed from the environment. (b) What are the values of ΔH and ΔU for the reaction? 1 L-atm = 101.3 J (6%) 3. The combustion of methylhydrazine (CH6N2) with oxygen produces N2(g), CO2(g), and H2O(l): CH6N2(l) + O2(g) → N2(g) + CO2(g) + H2O(l) (unbalanced) When 4.00 g of CH6N2 is combusted in a bomb calorimeter, the temperature of the calorimeter increases from 25.0 ℃ to 39.5 ℃. The heat capacity of the calorimeter is measured to be 7.79 kJ/℃. (a) What is the molar heat of combustion of CH6N2? (b) Balance the chemical reaction first. (4%) 4. The minimum energy required to cause the photoelectric effect in potassium metal is 3.69 x 10^-19 J. (a) What is the threshold frequency of potassium to produce the photoelectric effect? (b) What is the wavelength in nm? (c) Will photoelectrons be produced when visible light shines on the surface of potassium? (d) If 400 nm radiation is shone on potassium, what is the kinetic energy of the ejected electrons? (8%) 3+ 5. (a) Write ground-state electron configurations for Co ion and (b) is the ion paramagnetic or diamagnetic? (8.59, 4%) 6. (a) Balance the chemical reaction of the following: CH3OH(g) +O2(g) → CO2(g) + H2O(g) (b) Use bond energies to estimate the enthalpy change for the reaction. (c) Calculate the enthalpy of reaction from the standard enthalpies of formation of the reactant and product molecules. (6%) http://ppt.cc/XfC1 http://ppt.cc/HAt1 - 7. (a) Draw three resonance structures for the NO3 ion. (b) Indicate the formal charges of each atom. (c) Describe the hybrid orbitals used by the central atom. - (d) Predict the geometry of the NO3 ion. (e) What is the bond order of N-O? (11.21, 10%) 8. Using the molecular orbital model, (a) draw the energy level diagram, (b) write the electron configuration, (c) determine the bond order, and (d) indicate the magnetic property of C2 (that is diamagnetic or paramagnetic). (e) Show the HOMO-LUMO energy gap in C2 MO diagram. - (f) Compare the bond length with that of C2. (11.37, 12%) 9. Calculate the (a) molality, (b) molarity, and (c) mole fraction of NH3 in an 8.00 mass% aqueous solution (d = 0.9651 g/mL). (13.55, 6%) 10.A solution contains 1.00 mol of CH2Cl2 and 1.00 mol of CCl4 at 23.5 ℃. The vapor pressures of pure CH2Cl2 and CCl4 at 23.5 ℃ are 352 torr and 118 torr, respectively. (a) Assuming ideal solution behavior, calculate the partial pressures of CH2Cl2 and CCl4 over the solution. (b) What is the total vapor pressure? (c) Calculate the mole fraction of CH2Cl2 and CCl4 in the vapor above the solution? (d) Which component is more volatile, CH2Cl2 or CCl4? (e) Using fractional distillation to separate two components of the solution, which one (CH2Cl2 or CCl4) will be distilled out first? (13.83, 10%) --

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