課程名稱︰物質與能量平衡
課程性質︰必修/選修
課程教師︰諶玉真
開課系所︰化工系
考試時間︰2006/6/13 1:20~3:10
試題 :
1.Humid air enclosed in a 2.00-liter flask at 40。C.The flask is slowly cooled.
When the temperature reaches 20。C,drops of moisture become visible on the
flask wall.Although the pressure in the flask changes when the temperature
drops,it remains close enough to 1 atm for the psychometric chart to provide a
close representation of the behavior of the system throughout the process.Use
the chart to solve the following problems.
(a)What were the relative humidity,absolute humidity,and wet-bulb temperature
of the air at 40。C？
(b)Calculate the mass of the water in the flask.
(c)Calculate the enthalpy change in joules undergone by air in going from 40。C
to 20。C
2.One hundred g-moles per hour of liquid toluene at 25。C and 7 bar is
vaporized and heated to 300。C at constant pressure.Neglecting the effect of
pressure on enthalpy,estimate the rate at which heat must be applied.
Gas constant R = 0.08314 bar‧L / (mol‧K) = 8.314K / (mol‧K)
3.A vapor mixture containing 30 mole％ benzene and 70％ toluene at 1 atm is
cooled isobarically in a closed container from an initial temperature of 115。C
.Use the Txy diagram to answer the following questions.
(a)At what temperature does he first drop of condensate form？What is its
composition？
(b)At one point during the process the system temperature is 100。C.Determine
the mole fractions of benzene in the vapor and liquid phases at the point and
calculate the ratio(mole vapor/mole liquid).
(c)At what temperature does the last drop of condensate form？What is its
composition？
4.Values of specific internal energy of bromine at three conditions are listed
here.
┌──────┬──────┬───────┬───────┬──────┐
│ State │ T(K) │ P(bar) │ V(L/mol) │ U(kJ/mol) │
├──────┼──────┼───────┼───────┼──────┤
│ Liquid │ 300 │ 0.310 │ 0.0516 │ 0 │
├──────┼──────┼───────┼───────┼──────┤
│ Vapor │ 300 │ 0.310 │ 79.94 │ 28.24 │
├──────┼──────┼───────┼───────┼──────┤
│ Vapor │ 340 │ 1.33 │ 20.92 │ 29.62 │
└──────┴──────┴───────┴───────┴──────┘
(a)What reference state was used to generate the listed specific internal
energies？
(b)Calculate the specific internal energy change (kJ/mol) for a process in
which bromine vapor at 300L is condensed at constant pressure.To calculate the
specific enthalpy change for 5.00 mol of bromine undergoing the process.
(c)Bromine vapor in a 5-liter container at 300K and 0.205 bar is to be heated
to 340K.Calculate the heat (kJ) that must be transferred to the gas to achive
the desire temperature increase,assuming that the internal energy is
independent of pressure.
(d)In reality,more heat than the amount calculated in part(c) would have to be
transferred to the container to raise the gas temperature by 40K,for several
reasons.State two of them.
5.Superheated steam at T1(。C) and 10.0 bar is combined with saturated steam at
T2(。C) and 5 .0 bar in a ratio (2.56 kg of steam at 10 bar)/(1.0 kg of steam
at 5.0 bar).The product steam is at 250。C and 5.0 bar.The process operates at
steady state.
(a)Calculate T1 and T2,assuming that the mixer operates adiabatically.
(b)If in fact heat is being lost from the mixer to the surroundings,is your
estimate of T1 too high or too low?Briefly explain.
後面附錄表格：
(反正就是解題用的到的表格都會給了啦Orz)
Elementary principles of chemical process
by Richard M.Felder & Ronald W.Rousseau
書中的
Table B.1
Table B.2
Figure6.4-1(Txy and Pxy diagrams for benzene-toluene system.)
Table B.7
Figure8.4-1( Psychometric chart-SI units.Reference states:H2O(L,0。C,1atm),dry
air(0。C,1atm). )
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