課程名稱︰物理化學一 課程性質︰必修 課程教師︰李弘文 開課學院：理學院 開課系所︰化學系 考試日期（年月日）︰2010/8/22 考試時限（分鐘）：120 是否需發放獎勵金：是 （如未明確表示，則不予發放） 試題 : Read these instructions carefully before you start!! 1.This exam has total 8 pages. There are 3 parts, with total 100 points. 2.Answer directly on this exam. Only the answer shown in the assigned boxes will be graded. 3.Formula/constant sheet are given at the end of this exam. 4.No other notes/sheets can be used in this exam. 5.You can only use your own calculator. 6.When instructed to use specific constants in the question for calculation purpose, follow that instruction. 7.Correct answers must be accompanied with the correct sign and unit. 8.If you write this exam with pencil, you are not eligible for any re-grade. 9.You must show all the intermediate steps in how you work out the answers to the questions in part B and C. Part A:True or False questions(50 points, 2 point for each question) For the statement to be true, it must be always true. If the statement is false, simply circle the wrong statement or correct the statement to make it t true. 2 points for each correct answer, and 1 point will be subtracted from each incorrect answer. (a).The ratio of the most probable speed to the mean speed has the same value for all gases at all temperatures. (b).The mean speed of N2 gas is 50 m/s at room temperature. (c).If a probability distribution function is p(x)=(1/a), for 0,x,a,and zero otherwise, the <x>=a/3 (d).Using reduced variables, law of corresponding states can be used to describe H2 and HF gases without deviation. (e).Given Boyle's temperature can be written in van der Waals constants, TB=a/Tb, H2 has much smaller boyle's temperature than He. (f).NH3(g) is expected to have larger van der Waals coefficient a than CH4(g). (g).Maxwell construction can be used to correct the van der Waals loop when T>Tc. (h).When the compression factor (z) is larger than 1, The gas is more compressible than the ideal gas. (i).The second viral coefficient B describes the molar volume difference between real gas and ideal gas. (j).At a given temperature and volume, the pressure of a real gas is always less than the pressure of an ideal gas. (k).An intermolecular interaction with stabilizing energy of 10-21 J/molecule is stable at room temperature. (l).Area under heat capacity-temperature(C vs T) curve equals heat. (m) (6xy3dx+9x2y2dy) is an exact differential. (n).Joule's free expansion experiment is a constant enthalpy process. (o).To liquefy real gas, it is necessary to prepare gas within the temperature and pressure range that Joule-thomson coefficient is positive. (p).The standard enthalpy of formation for CO2(g) is higher at 500 K than at 298.15 K (送分) (q).The enthalpy of a system is never smaller than its internal energy. (r).In the reversible adiabatic expansion of a real gas, the enthalpy always decreases. (s).The work done by a gas in an irreversible expansion from state 1 to state 2 is always less than the work done by a gas in a reversible expansion from state 1 to state 2. (送分) (t).The entropy of the surrounding must increase when an irreversible process occurs . (u).The entropy of an isolated system remains constant when a reversible process occurs in the system. (v).An ideal gas expands adiabatically into a vacuum leads to the drop in temperature. (w).Heat pumps is used to heat up the house to 25oC in the winter. It's efficiency is better when the outdoor temperature is lower. (x).Knowing that liquid bromine does not have strong intermolecular interactions, and its molar enthalpy of vaporization is 28 kj/mol, it is reasonable to estimate that it boils around 91oC. (y).dS-CpdT/T for any reversible process. Part B:Short calculation questions (30 points, 5 points each) 1.What fraction of oxygen molecules at 300 K have velocities between 500 and 510 ms^-1? You can assume that F(v) is independent of v in this intervals. 2.At critical point, (dP/dV)Tc=0, (d^2p/dV^2)Tc-0. Derive the expressions for van der Waals constants a and b in terms of the critical temperature and pressure (Tc and Pc) 3.A mole of monoatomic ideal gas at 1 bar and 300 K os allowed to expand adiabatically against a constant pressure of 0.5 bar until equilibrium is reached. (a)What is the final volume? (b)How much work is done on the gas in this process? 4.For a 1 mole van der Waals gas, calculate the change og q,w and U during a reversible isothermal expansion from V1 to V2. (dU/dV)T=an^2/V^2 5.Ammonia (considered to be an ideal gas) initially at 25oC and 1 bar pressure is heated at constant pressure until the volume have doubled. calculate (a) q per mole (b) w per mole (c) delta H (d) delta U (e) delta S given Cp=25.895+32.999x10^-3xT-30.46x10^-7xT^2 JK^-1mol^-1 6.What is molar entropy change of the following process: Steam (100oC , 1 bar) >>> ice (0oC, 1 bar) consider that the average specific heat of liquid water is a constant of 4.2JK^-1g^-1. The enthalpy of vaperization at the boiling point and the enthalpy of fusion at the freezing point are 2258.1 and 33.5Jg^-1, respectively. PartC:Long questions (20 points total, Show your work for partial credit) (A). (1o pts) Description question (A1). (4pts) Explain why it's impossible to design a heat engine with efficiency better than the reversible Carnot engine. (A2). (3 pts) Step 1:adiabatic compression Step 2:isothermal compression Step 3:adiabatic expansion Stpe 4:isothermal expansion (A3). (3 pts) Assuming Cp is a constant. Step 1:isothermal expansion Step 2:heating at constant pressure Step 3:isothermal compression Step 4:colling at constant pressure (B). (10 pts, 2 pts each) Consider doing the joule-Thomson (J-T) experiment for a non-ideal gas: 1 mole gas (3.oo bar, 293.15 K, 7.787 L) >>>1 mole gas(1.00 bar, 290.87 K,23.920 L)......(i) Cp is a constant of 37.1 J/(K-mol),and the compressibility factor Z is a constant at the same temperature. (B1). Calculate delta H and delta U for the change of states (i) in this J-T process (B2). Calculate V3. --

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