课程名称：普通化学丙 课程性质︰必修 课程教师︰刘铭璋 开课学院：理学院 开课系所︰化学系 考试日期（年月日）︰2015/1/14 考试时限（分钟）：110 mins 试题 : Final Exam of General Chemistry 1/14/2015 1.Which one of the following statements is/are true for a concentration cell? (4%) a.A concentration cell is in which both compartments have the same components but at different concentration. b.The best concentration cell will consist of the substance having the most positive standard reduction potential. c.It is an electrolytic cell. d.ε°= 0 V e.The electrons flow is in the direction that tends to equalize the concentrations. f.The standard reduction potentials are dependent on concentration. g.Oxidation occurs at the anode and is where anions move towards. 2.Which of the following statements concerning electrochemistry is/are true? (3%) a.Corrosion is an example of an oxidation-reduction process. b.Corrosion of steel involves the reduction of iron coupled with the oxidation of oxygen. c.When a battery dies,ΔG = 0 and Q = K. d.Aluminum does not corrodes as does iron, because a protective layor of Al2O3 forms on the metal surface. e.The key to cathodic protection is to connect via a wire a metal more easily reduced than iron to the steel surface to be protected. 3.Which of the following statements concerning electrochemistry is/are true? (4%) a.The mass of a nucleus is always more than the sum of the masses of the nucleons. b.Electron capture is likely when the neutron-to-protron ratio in a nucleus is too low. c.Nuclei with even numbers of both protons and neutrons are usually more stable than those with odd numbers of neutrons and protrons. d.All isotopes of technetium(Tc,Z=43) are radioactive. e.All isotopes of the elements with atomic numbers lower than 83 are radioactive. f.In order for fisson reactions to occur,temperatures must be in the millions of degrees. g.As atomic mass increases,the neutron/proton ratio of stable nuclides decreases. h.Nuclides that are not already in the zone of stability undergo radioactive processes to get to the zone of stability. i.Fusion occurs among the heaviest isotope,whereas fission occurs more readily for light isotopes. j.The so-called "magic numbers(2,8,20,28,50,82,and 126)" of protons and neutrons produce special nuclear stability. 4.Which of the following statements concerning radation is/are true?(3%) a.The higher the energy content of the radiaton,the more damage it can cause. b.The penetrating power is alpha>beta>gamma. 90 c.Contamination of the environment with 38Sr poses serious health hazards because of the similar chemistry of strontium and calcium. d.The rate of radioactive decay processes,like the rates of chemical reactions, are sensitive to temperature and pressure changes. e.The SI unit of dose equivalent is Sievert, Sv. 5.Which of the following statements concerning nuclear reactor is/are true?(5%) a.Control rods,composed of substances that absorb neutrons,are used to regulate the power level of the reactor. b.D2O is commonly used as moderators in a light-water reactor. c.Reactor core is the part of a nuclear reactor where the fission reaction takes place. d.Breeder reactor is a nuclear reactor in which more fissionable fuel is produce while reactor runs. e.Nuclear chain reaction is a self-sustaining fission process caused by the production of neutrons that proceed to spilt other nuclei. f.The isotope that undergoes fission in a nuclear reactor is U-238. g.Nuclear reactions release far more energy(by a factor of one million or more) for comparable amounts of reactants. 6.Consider the following decay series: 218 a 214 b 214 c 214 d 210 Po ——→ Pb ——→ Bi ——→ Po ——→ Pb 84 82 83 84 82 Which type of nuclear process occurs in steps c and d,respectively?(2%) (1)α emission,α emission (2)α emission,β emission (3)β emission,positron emission (4)β emission,α emission (5)positron emission,β emission 7.What fraction of radioactive atoms remains in a sample after six half-lives? (2%) (a) zero (b) 1/6 (c) 1 (d) 1/32 (e) 1/64 8.For which process are ΔS positive?(4%) a.evaporation of 1 mol of CCl4(l) b.mixing 4 mL of ethanol with 26 mL of water c.compressing 1 mol of Ne at constant temperature from 1.0 atm to 2.2 atm d.raising the temperature of 10 g of Cu from 276K to 294K e.grinding a large crystal of KCl to powder 9.Which one of the following reactions would you expect to have the lowest ΔS° ?(2%) rxn a.CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) b.C2H2(g) + 5/2O2(g) → 2CO2(g) + 2H2O(g) c.C2H4(g) + O2(g) → 2CO2(g) + 2H2O(g) d.C2H6(g) + 7/2O2(g) → 2CO2(g) + 3H2O(g) 10.Which of the following statements concerning thermodynamics is/are true? (10%) a.NaCl(s) perfectly ordered crystal at 298K is expected to have zero entropy. b.Na(s) at 298K is expected to have zero enthalpy(ΔHf°= 0 ) c.With respect to the system only,a reaction with ΔH>0 and ΔS<0 is predicted to be nonspontaneous at all temperatures. d.For any pure substance,if ΔHf°= 0 and ΔGf°= 0,then S°= 0 e.The change in enthlapy,ΔH,for a process is equal to the amount of heat absorbed at constant pressure, qp. f.A bomb calorimeter measures ΔH directly. g.Entropy is state function. h.Second of thermodynamics states that for any spontaneous process there is always an increase in the entropy of the system. i.In any real process,w < w max. j.Thermodynamics can predict the rate at which a system will spontaneously change. 11.Consider the following diagram of free energy (G) versus fraction of A reacted for the reaction A(g)→B(g) ← ↑∣ iii ╱ ∣∣ ╱ ∣∣ i ╱ G ∣ ╲ ╱ ∣∣ ╲ ╱ ∣∣ ╲╱ ∣∣ ii └──────────── 0 0.5 1.0 Fraction of A reacted Which of the following statements is/are true?(8%) a.For this reaction,ΔG°> 0 b.At point i,ΔGi < 0.The system will move to the right to reach equilibrium. c.At point iii,ΔGiii < 0.The system will move to the right to reach equilibrium. d.K < 1 for this reaction e.ΔGii = 0.The system is at equilibrium. f.K can be calculated by ΔGii. g.Equilibrium lies closer to products. 12.Sketch the galvanic cell based on the following half-reactions. MnO4- + 8H+ + 5e- → Mn2+ + 4H2O ε°= 1.51 V IO4- + 2H+ + 2e- → IO3- + H2O ε°= 1.60 V Show the direction of electron flow,show the direction of ion migration through the salt bridge,and identify the cathode and anode.Give the overall balanced equation,and determine ε°for the galvanic cell.Which species is reducing agent?Give the standard line notation for the cell.Calculate the maximum amount of work that can be obtained from the galvanic cells at standard conditions.Calculate εcell at 25°C when [MnO4-]=2.1M,[H+]=1.0M,[Mn2+]=2.1M [IO4-]=0.9M,[IO3-]=0.9M.F=96485 (14%) 13.Balance the following oxidation-reduction reaction that occurs in basic solution. NO2-(aq) + Al(s) → NH3(g) + AlO2-(aq) (4%) 235 14.(a)Calculate the binding energy in J/nucleon for 92U(atomic mass 235.0439). 1 The atomic mass of 1H is 1.00782 amu and the mass of a neutron is 1.00866 amu. 56 (b)The most stable nucleus known is Fe.Would the binding energy per nucleon 56 235 for Fe be larger or smaller than that of U?(1J=1kg*m^2/s^2) (8%) 15.The standard free energies of formation and the standard enthalpies of formation at 298K for difluoroacetylene(C2F2) and hexafluorobenzene(C6H6) are ΔGf°(kJ/mol) ΔHf°(kJ/mol) ───────────────────────────── C2H2(g) 191.2 241.3 C6H6(g) 78.2 132.8 For the following reaction : C6H6(g) → 3C2H2(g) ← a.calculate ΔS°,ΔH°,ΔG°at 298K. b.calculate K at 298K. c.estimate K at 3000K,assuming ΔH°and ΔS°do not depend on temperature.(11%) 16.Given the following data P4(s) + 6Cl2(g) → 4PCl3(g) ΔH = -1225.6 kJ P4(s) + 5O2(g) → P4O10(s) ΔH = -2967.3 kJ PCl3(g) + Cl2(g) → PCl5(g) ΔH = -84.2 kJ PCl3(g) + 1/2O2(g) → Cl3PO(g) ΔH = -285.7 kJ calculate ΔH for the reaction P4O10(s) + 6PCl5(g) → 10Cl3PO(g) ΔH = ? (8%) 17.A ballon filled with 39.1 mol helium has a volume of 876 L at 1.00 atm pressure.The ballon absorbs 30.9 kJ of heat as it expands to a volume of 998 L,the pressure remaining constant.Calculate q,w,and ΔE for the helium in the ballon. 1 L*atm = 101.3 J (8%) --

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