课程名称︰物理化学上 课程性质︰必修 课程教师︰苏志明 开课学院：生农学院 开课系所︰农业化学系 考试日期（年月日）︰2009 10 22 考试时限（分钟）：130 是否需发放奖励金：是 试题 : 1.Consider an aqueous solution of alanine amino acid(CH(CH3)(NH3+)(COO-)). The proton dissociation constants for the carboxylic group and the protonated amino group are pK1(-COOH)=2.35, and pK2(-NH3+)=9.87, respectively. (a)What is the isoelectric point for a compound like the amino acid alanine? In other words, explain the isoelectric point. (b)With the above acid-base equilibrium constants, derive and calculate the isoelectric point for this amino acid in water. 2.For 1 mole of ideal gas at 298K, calculate its total kinetic energy of the gas molecules. 3.(a)For 1 mole of ideal gas undergoing a reversible isothermal expansion form the initial state of (P1,V1) to a final state of (P2,V2), calculate the work and heat the system generates in this process. The system temperature is set at T. (b)If a free expansion instead of the reversible isothermal expansion was carried out in(a), calculate the accompanied work and heat in this process. 4.The mass percentage of dry air is approximately 75.5% for nitrogen, 23.2% for oxygen, and 1.3% for argon. What is the partial pressure of each gas when the total pressure is 1 atm? To calculate the mole fractions use densities of 28.02, 32.0, and 39.9 g mol^-1 for nitrogen, oxygen, and argon respectively. 5.The carbon dioxide gas actually follows the van der Waals equation with the van der Waals constants a=3.6 L^2 atm mol^-2 and b=0.043 L mol^-1. Assuming a temperature of 298 K and a volume of 25L, calculate the pressure of 1 mole of carbon dioxide gas. 6.Consider the combustion reaction of the hydrogen gas: H2(g) + 1/2 O2(g) ←→ H2O(g) With the help of the related thermodynamic data listed below, answer the following questions: (a)Calculate △S°, and △H°of this reaction at 298K and a constant pressure of 1.00 atm. (b)Calculate △S°,and △H°of this reaction at 1000K and a constant pressure of 1 atm. (c)Calculate the theoretical maximum temperature that could be reached by igniting a mixture of 1 mole of hydrogen and 0.5 mole of oxygen under 1 atm constant pressure (i.e. a hydrogen-oxygen flame or burner). The initial system temperature is 298K. (Hint: use Hess's law to set up a working reaction path) (d)The same question as in (c), except that we ignite a mixture of 1 mole of hydrogen and 2.5 mole of the air under 1 atm constant pressure (i.e. a hydrogen-air flame). The air consists of 20% of oxygen and 80% of nitrogen (in mole fraction), and the initial system temperature is 298K. ----------------------------------------------------------------------------- Related thermodynamic data: (i)Molar heat capacities at constant pressure (J/mol．K)(Assuming that they are constant over the temperatures we considered): H2(g)=28.9 O2(g)=29.5 N2(g)=29.0 H2O(g)=24.8 H2O(l)=75.2 (ii)Thermodynamic data at 298K Substance △H°f △G°f S° (kJ/mol) (kJ/mol) (J/K．mol) H2(g) 0 0 131 O2(g) 0 0 205 H2O(g) -242 -229 189 H2O(l) -286 -237 70 ------------------------------------------------------------------------------ 7.A sealed 1-L glass container at 1 atm and 25℃ is heated and breaks when the internal pressure reaches 2 atm. When it breaks what is the temperature inside and what is the internal energy? Assume that the specific heat of air has the value of Cv = 25 J/(K．mol). 8.Consider two blocks of copper with the same mass M. Assuming that one of them is at a temperature of Tc and the other at Th with Th > Tc. The constant pressure molar heat capacity is represented by Cp. what is the total entropy change when these two blocks of copper are brought together and are in thermal equilibrium with each other? xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Some equations and constants: (i)van der Waals equation: (P+a/V^2)(V-b) = RT (ii)1L．atm = 24.2 cal; 1cal = 4.18J; R = 0.082 L atm deg^-1 mol^-1 = 8.31 J K^-1 mol^-1 --

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