课程名称︰普通化学丙 课程性质︰必修 课程教师︰周必泰 开课学院：医学院/电资学院 开课系所︰医学系/牙医学系/电机系 考试日期（年月日）︰2018/01/12 考试时限（分钟）：170 试题 : General Chemistry (Total Score 220) Midterm Examination 2017/11/17 1. Questions in midterm exam 1-1. In infrared spectra, the absorption band of C=O is at about 1700 cm^(-1), but the absorption band of C-H is at about 3000 cm^(-1). Please explain why the absorption frequency of C-H is higher than C=O but with much lower bond energy. (10) 1-2. Thermal energy could be in a form of kT where k is the Boltzmann's constant (1.38 × 10^(-23) JK^(-1)), T is in Kelvin (K). Please convert temperature 1K (or 1℃) thermal energy in terms of kcal/mol (5). 298 K is generally considered to be room temperature. Calculate the associated thermal energy. (5) 1-3. (a) Draw MOs of B2 and O2 and Explain why both B2 and O2 are paramagnetic (10). (b) Arrange the ionization energy of O2, O2-, O2+ by increasing trend (5) (c) A Lewis structure obeying the octet rule can be drawn for O2 as follows: .. .. Ｏ＝Ｏ .. .. Use the molecular orbital energy-level diagram for O2 to show that the above Lewis structure corresponds to an excited state. (5) 2. Definition and Explanation (after midterm exam) 2-1. Define superfluid (5), and write down any applications of CO2 and H2O superfluid (5) 2-2. In the phase diagram for water (see below), explain why the slope of point C to O line between solid phase and liquid phase is negative, whereas most of other materials are positive? (5) Define physical meaning of point O and point A (5). https://i.imgur.com/VXlRqaL.png 2-3. Using the band gap theory to explain the_conductor, semiconductor and insulator (10). Upon increasing temperature, predict the changes of the conductivity for these three types of materials and explain (5). 2-4. Define p type and n type semiconductors (5). Put materials Ga As and 0.6 0.4 Ga As together, please specify which is p and which is n type (5). 0.4 0.6 Briefly describe p-n junction and its application in light emitting diode (5) or rectifier (5). Define Fermi energy level (5). 2-5. Define (a) steady-state approach (5) (b) elementary step (5) (c) molecularity (5) (d) the difference between half-life and lifetime (5) 2-6. The Arrhenius equation for the reaction rate can be generally expressed as -Ea/RT -Ea/RT k = zpe . Please explain the definition of z,p and e (5). Which -Ea/RT parameter z,p or e is changing when the catalyst is added? (5) 2-7. The graph below shows the number of collisions with a particular energy for two different temperatures. https://i.imgur.com/IvfD5Qi.png a. Which is greater, T2 or T1? How can you tell? (5) b. What does this graph tell us about the temperature dependence of the rate of a chemical reaction? Explain. (5) 3. Question 3-1. The standard enthalpy of formation of H2O(l) at 298K is -285.8kJ/mol. Calculate the change in internal energy for the following process at 298K and 1 atm: (10) H2O(l) → H2(g) + 1/2 O2(g) 3-2. An isothermal process is one in which the temperature of the system and surroundings remain constant at all times. With this mind, what is wrong with the following statement : "for an isothermal expansion of an ideal gas against a constant pressure, ΔT = 0, so q = 0" ? What is q equal to in an isothermal expansion of an ideal gas against a constant external pressure? (10) 3-3. Cubic packing spheres are stacked on top of each other in successive layers. Define volume occupied by spheres in the unit cell f_v = ─────────────────────── volume of the unit cell prove f_v = 52.4% for a cubic packing (10). 3-4. Considering two Bricks with two different temperatures and different molar heat capacity (Cp) shown below: ┌────╥────┐ │ ║ │ │ Cp1,T1 ║ Cp2,T2 │ │ ║ │ └────╨────┘ Assuming T1 > T2, based on the second law of thermodynamics to predict the direction of the flow of the heat when two bricks are contacted. Assuming Cp1 and Cp2 are both temperature independent, what is the final temperature after connecting these two bricks? (Assuming one mole for each brick) (10) 3-5. (a) Write down the definition of thermodynamic parameters G and H . Then, derive the following relationship (10) dG = VdP - SdT dH = TdS + VdP in which P, V and T denote pressure, volume and temperature, respectively, and S is system entropy at 25°C (b) Explain why you need to make diamond from graphite at high pressure and decent temperature (5) https://i.imgur.com/RRzAjFV.png 3-6. The reaction between NO and H2 may proceed via the following mechanism (single answer) k_-1 1. 2NO ⇋ N2O2 k1 k2 2. N2O2 + H2 → N2O + H2O Apply the steady-state approximation for N2O2, express the rate of H2 depletion in (a) very low H2 concentration, (b) very high H2 concentration and (3) medium H2 concentration. (15) 3-7. The van't Hoff equation is expressed as 0 K2 -ΔH 1 1 ln─ = ───(─ - ─) K1 R T2 T1 0 where K1 and K2 are equilibrium constants at T1 and T2, respectively, ΔH is the standard enthalpy change of the reaction. Please derive this 0 -6 equation from ΔG (5). Kp is 3.7×10 at 900K for the ammonia synthesis -3 reaction. Assuming the value of Kp is 8.2×10 at 500K. Calculate the reaction enthalpy ΔH (5) ◎ 口头说明 2-4. light emitting diode (发光二极体); rectifier (整流器); or 的意思是两者都要回答 ◎ 投影补充 3-7. R = 8.314 J K^(-1) mol^(-1) --

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