课程名称︰化工热力学甲一
课程性质︰化工系必修
课程教师︰林祥泰
开课学院：工学院
开课系所︰化工系
考试日期（年月日）︰2014/01/07
考试时限（分钟）：120min
是否需发放奖励金：是
（如未明确表示，则不予发放）
试题 :
Final Exam
Closed book and notes
Note: The values in square brackets after eachquestion are credit points for
each problem. Totally 100 points.
1.The following set of reactions is thought to occur between nitrogen and
oxygen at high pressures
N2 + 1/2O2 = N20
N2 + O2 = 2NO
N2 + 2O2 = N2O4
N2O4 = 2NO2
N2O + NO2 =3NO
(a) Find an independent set of reactions for the nitrogen-oxygen system. [6]
(b) How many degrees of freedom are there for this system. [2]
(c) If the starting oxygen-to-nitrogen ratio is fixed(as in air), how many
degrees of freedom are there? [2]
2.A mixture of gas containing 10 mol% of n-butane and 90 mol% of n-pentane is
originally at 1 atm and 140°C. The mixture is compressed isothermallym to a
point where condensation occurs. The vapor pressures of n-butane and n-pentane at
at 140°C are 29.756 atm and 13.86 atm, respectively. Assuming ideal mixtures
in both the vapor and liquid phases,
(a) What is the pressure when the first drop condenses? What is the composition of i .
of that drop? [10]
(b) What are the pressure and vapor compositions when the last drop condenses?
[10]
3. The activity coefficient of a binary mixture can be described in terms of
the van Laar model as
lnγ1=α/(1+α*x1/β*x2)^2 lnγ2=β/(1+β*x2/α*x1)^2
where α and β are constants, x1 and x2 are the mole fractions of components
1 and 2,respectively. The vapor pressure of the two components are P1vap and
P2vap,respectively
(a) Find the expression of the partial molar excess Gibbs free energy of
components 1 and 2, respectively. [2]
(b) Find the expression ot activity of components l and 2, respectively. [2]
(c) Find the expression of fugacity of components 1 and 2, respectively. [2]
(d) Find the expression of the Henry's law constants for components 1 and 2,
respectively. [2]
(e) Find the expression of the molar excess Gibbs free energy of the mixture.
[2]
(f) Find the expression of the Gibbs free energy of mixing. [2]
(g) Find the expression of the enthalpy of mixing. [2]
(h) Find the expression of the entropy of mixing. [2]
(i) Show that the parameters α and β can be determined from the activity
coefficient as α=lnγ1[1+(x2lnγ2)/(x1lnγ1)]^2
and β=lnγ2[1+(x1lnγ1)/(x2lnγ2)]^2
[4]
4. The vapor-liquid equilibrium of a binary mixture at 45°C is given as the
P-X-Y diagram on the right.
图片网址 http://ppt.cc/qud~
(a) What is the vapor pressure of components 1 and 2, respectlvely?[2]
(b) What is the presure and composition of azeotropic mixture at 45°C?[2]
(c) Describe the state of aggregation (i.e. vapor, liquid, or solid) and
composition of each component of mixtures at points A, B, ..., to H. [16]
(d) Estimate the fugacity of components 1 and 2, respectively,at points
A, B, ..., to H. [16]
(e) Determine the activity coefficient of components 1 and 2, respectively,
for the mixture at points C. What is the mininum work necessary to
separate 1 mole of this mixture to pure 1 and 2 under the same
temperature and pressure? [6]
(f) Determine the activity coefficient of components 1 and 2, respectively,
for the mixture at points F. What is the minimum work necessary to
separate l mole of this mixture to pure 1 and 2 under the same
temperature and pressure? [6]
(g) Use the data at the azeotropic point, determine the parameters α and β in
the van Laar model (see problem 3). [2]