課程名稱︰普通化學乙 課程性質︰必修 課程教師︰佘瑞琳 講師 開課學院：工學院 開課系所︰土木工程學系 考試日期（年月日）︰2009-04-17 考試時限（分鐘）：110分鐘 是否需發放獎勵金：是 （如未明確表示，則不予發放） 試題 : 黃色代表上標綠色代表下標亮白代表粗體 題目有圖 General Chemistry Mid-term Exam 4/17/2009 R=8.314 J/mol.K = 0.082L.atm/mol.K Atomic mass (g/mol) : F = 19.0, Ne = 20.2, O = 16.0, N = 14.0, C = 12.0, H = 1.0, He = 4.00, Cl = 35.5 I. Multiple choices question (40%, 2 points for each question) 1. Which of the following ordering is correst? (a) radius: N atom < N3- ion (b) radius: Mg aton < Mg2+ ion (c) ionic redius: F- < Na+ (d) lattice energy: NaCl < NaF < MgF2 2. Which of following ranking is correct? (a) bond polarity: F-F < O-F < C-F (b) bond energy: F-F < O-F < C-F (c) energy gap: Ca < Si doped with B < Si < I2 (d) conductivity at room temperature: Ca < Si dopes with B < Si < I2 3. For DuPont's Freon-12, CF2Cl2 (a) It is one of CFCs (chlorofluorocarbons). (b) It has a square planar geometry. (c) It is chemically inert. (d) It is the monomer of Teflon (polytetrafluoroethylene) 4. Which fo the following molecule is nonpolar? (a) BF3 (b) IF3 (c) NH3 (d) BeF2 5. Which of the following substance shows H-bonding? (a) CH3OCH3 (b) CH3OH (c) CH3COOH (d) H2S 6. For the face-centered cubic, which of following statement is correct? (a) The coordination number is 4. (b) There are 4 atoms in a unit cell. (c) It is one of closest packing. (d) The packing efficiency is the highest among cubic systems. 7. A certain solid substance characterized by low melting point and extremely low electrical conductivity is? (a) S8 (b) MgO (c) Cu (d) diamond 8. Which of the following ordering is correct? (a) vapor pressure: CH3COCH3 < CH3CH2CH2OH (b) normal boiling point: CF4 < CCl4 (c) viscosity: CH3CH2OH < CH2OHCH2OH (d) critical temperture: CO2 < H2O 9. For the polymer Kavlar, http://0rz.tw/kYC33 (a) This is an addition polymer. (b) This is a polyamide (c) http://0rz.tw/CheXY is one of the monomers. (d) http://0rz.tw/1zZuW is one of the monomers. 10. According to the phase diagram of carbon dioxide, http://0rz.tw/PFRn6 (a) The critical temperature is 31.1oC (b) Point X is the melting point. (c) Point Y is the normal boiling point. (d) The density of solid CO2 is greater than liquid CO2 11. What is the coordination number of atoms in the diamond structure? (a) 2 (b) 4 (c) 6 (d) 8 12. Which of the following is extensive property? (a) density (b) internal energy (c) enthalpy change (△H) (d) melting point 13. If 515 J of heat are added to a gas that does 218J of work as a result, (a) the heat transferred is +515J (b) the work done by system is +218J. (c) the internal energy change of the system is +733J (d) this is an endothermic reaction. 14. A quantity of gas is confined in a piston at 20oC. The initial volume is 0.050 L and the pressure is 1.0 atm. It undergoes a constant-temperature expansion aganist a constant pressure of 0.20 atm to final volume of 0.25L. Calculate the work (w) done by the gas. (a) w = -0.20 L.atm (b) w = +0.20 L.atm (c) w = -0.040 L.atm (d) w = +0.040 L.stm (e) None of the above. 15. Given the values of △Ho for the two reactions below, what is △Ho in kJ for the reaction: IF5(g) → IF3(g) + F2(g) IF(g) + F2(g) → IF3(g) △Ho = -390 kJ IF(g) + 2F2(g) → IF5(g) △Ho = -745 kJ (a) +355 (b) -1135 (c) +1135 (d) +35 (e) -35 16. Which of the following standard enthalpy of formation values is zero at 25oC? (a) F2(g) (b) Br2(g) (c) HF(g) (d) C(graphite) 17. Which of the following is exothermic reaction? (a) Solid iodine sublimes. (b) Nitrogen gas condenses to liquid nitrogen. (c) Water vaporizes. (d) Hydrochloric acid (HCl) mixed with barium hydorxide(Ba(OH)2) solution. 18. Carbon tetrachloride (CCl4) is a liquid at room temperature and pressurem whereas ammonia (NH3) is a gas. How can these observations be rationalized in trems of intermolecular forces? (a) NH3 is a polar molecule with higher dipole-dipole interation. (b) NH3 is has hydrogen bonding between molecules and shows higher intermolecule force. (c) CCl4 is a nonpolar molecule with much higher molecular mass than NH3 (d) Dispersion forces in CCl4 are stronger than the hydrogen bonding and dipole forces in the NH3 19. According to the pressure curves, choose the correct answer. http://0rz.tw/Hww4q (a) Substance (a) has the highest vapor pressure at 20oC. (b) Substance (a) has the highest normal boiling point. (c) Substance (a) has the greatest intermolecular forces. (d) Substance (a) has the highest enthalpy of vaporization. 20. Consider the following Lewis structure, which statement about the molecule is true? H O H H │ ║ │ │ H─C──C──C══C─H │4 3 2 1 H (a) There are 10 sigma and 2 pi bonds. (b) C-2 is sp2 hybridized with bond angles of 120o. (c) Oxygen is sp3 hybridized. (d) Bond angles of C-4 is 90o II. Problem (60%) 1. For the molecules, SF4 (a) draw the Lewis structure; (b) indicate the hybridization of the central atom, S; (c) determine the shape of the molecule. (d) Is this a polar or nonpolar molecule? (8%, p284) 2. For the diatomic molecule F2, (a) draw the molecular orbital energy level diagram, (b) write the electron configuration, (c) determine the bond order, and (d) indicate the magnetic properties (that is diamagnetic or paramagnetic). (e) Show the HOMO-LUMO energy gap in F2 molecule. (10%) 3. The spacing in a crystal lattice can be measured very accurately by X-ray diffraction, and this provides one way to determine Avogadro's number. One form of iron (atomic mass is 55.85) has a body-centered cubic lattice, and each side of the unit cell is 286.65 pm long. The density of the crystal at 25oC is 7.874 g/cm3. (a) What is the molar volume of iron? (b) Use these data to determine Avogadro's number. 1 pm = 1 ×10-12 m (10%, 8.21) 4. The crystal lattice for the ionic solid zinc sulfide is shown as figure. http://0rz.tw/T3SE1 (a) Calculate the number of Zn2+ and S2- ions in each unit cell. (b) How is the empirical formula of zinc sulfide based on crystal structure? (6%) 5. The heat capacity of a bomb calorimeter was determined by burning 6.79 g of methane (energy of combustion = -802kJ/mol CH4) in the calorimeter. The temperature changed by 10.8oC. (a) What is the heat capacity of the bomb calorimeter? (b) A 12.6g sample of acetylene, C2H2, produced a temperature increase of 16.9oC in the same calorimeter. What is the energy of combustion of acetylene (in KJ/mol)? (c) Is the internal energy of products higher or lower than reactants in the combustion reaction of acetylene? (10%) 6. Ethanol (CH3CH2OH) is one form of the biomass energy, which is mixed with gasoline to make gasohol. (a) Write the balanced combustion reaction of ethanol. (b) Calculate the heat of combustion from enthalpy of formation. (c) Estimate the heat of combustion from bond energy listed. (10%) Table 1 Standard enthalpy of formation at 25oC ┌──────┬────────┐ │ Compound │ △Hof(kJ/mol) │ ├──────┼────────┤ │ CH3CH2OH(l)│ -227.7 │ ├──────┼────────┤ │ CH3OH(l) │ -238.66 │ ├──────┼────────┤ │ CO2(g) │ -393.5 │ ├──────┼────────┤ │ H2O(l) │ -285.8 │ ├──────┼────────┤ │ CO(g) │ -110.5 │ └──────┴────────┘ Table 2 The average bond energy of covalent bonds. ┌───────┬──────────────┐ │Covalent bond │Average bond energy(kJ/mol) │ ├───────┼──────────────┤ │C ─ C │ 348 │ ├───────┼──────────────┤ │C ─ H │ 413 │ ├───────┼──────────────┤ │O ─ H │ 463 │ ├───────┼──────────────┤ │C ─ O │ 358 │ ├───────┼──────────────┤ │C ═ O │ 799 │ ├───────┼──────────────┤ │O ═ O │ 495 │ └───────┴──────────────┘ 7. Calculate △Ho for the conversion of graphite into diamond from the following equations. Write the balanced chemical reaction first. (9.56, 6%) C(s,graphite) + O2(g) → CO2(g) △Ho = -393.51 kJ C(s,diamond) + O2(g) → CO2(g) △Ho = -395.94 kJ ~end~ -- --

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