Chapter 13 | 7091.A. Bejan. Advanced Engineering Thermodynamics.2nd
ed. New York: Wiley Interscience, 1997.
2.Y. A. Çengel, Y. Cerci, and B. Wood, “Second Law
Analysis of Separation Processes of Mixtures,”ASME
International Mechanical Engineering Congress and
Exposition,Nashville, Tennessee, 1999.
3.Y. Cerci, Y. A. Çengel, and B. Wood, “The Minimum
Separation Work for Desalination Processes,”ASMEREFERENCES AND SUGGESTED READINGInternational Mechanical Engineering Congress and
Exposition,Nashville, Tennessee, 1999.
4.J. P. Holman. Thermodynamics.3rd ed. New York:
McGraw-Hill, 1980.
5.K. Wark, Jr. Advanced Thermodynamics for Engineers.
New York: McGraw-Hill, 1995.Composition of Gas Mixtures
13–1C What is the apparent gas constantfor a gas mixture?
Can it be larger than the largest gas constant in the mixture?
13–2C Consider a mixture of two gases. Can the apparent
molar mass of this mixture be determined by simply taking
the arithmetic average of the molar masses of the individual
gases? When will this be the case?
13–3C What is the apparent molar massfor a gas mixture?
Does the mass of every molecule in the mixture equal the
apparent molar mass?
13–4C Consider a mixture of several gases of identical
masses. Will all the mass fractions be identical? How about
the mole fractions?
13–5C The sum of the mole fractions for an ideal-gas mix-
ture is equal to 1. Is this also true for a real-gas mixture?
13–6C What are mass and mole fractions?
13–7C Using the definitions of mass and mole fractions,
derive a relation between them.
13–8C Somebody claims that the mass and mole fractions
for a mixture of CO 2 and N 2 O gases are identical. Is this
true? Why?
13–9C Consider a mixture of two gases Aand B. Show that
when the mass fractions mfAand mfBare known, the mole
fractions can be determined fromwhere MAand MBare the molar masses of Aand B.yAMB
MA 11 >mfA 12 MB¬and¬yB 1 yA
PROBLEMS*13–10 The composition of moist air is given on a molar
basis to be 78 percent N 2 , 20 percent O 2 , and 2 percent water
vapor. Determine the mass fractions of the constituents of air.
13–11 A gas mixture has the following composition on a
mole basis: 60 percent N 2 and 40 percent CO 2. Determine the
gravimetric analysis of the mixture, its molar mass, and gas
constant.
13–12 Repeat Prob. 13–11 by replacing N 2 by O 2.
13–13 A gas mixture consists of 5 kg of O 2 , 8 kg of N 2 ,
and 10 kg of CO 2. Determine (a) the mass fraction of each
component, (b) the mole fraction of each component, and
(c) the average molar mass and gas constant of the mixture.
13–14 Determine the mole fractions of a gas mixture that
consists of 75 percent CH 4 and 25 percent CO 2 by mass.
Also, determine the gas constant of the mixture.
13–15 A gas mixture consists of 8 kmol of H 2 and 2 kmol of
N 2. Determine the mass of each gas and the apparent gas con-
stant of the mixture. Answers:16 kg, 56 kg, 1.155 kJ/kg · K
13–16E A gas mixture consists of 5 lbmol of H 2 and
4 lbmol of N 2. Determine the mass of each gas and the appar-
ent gas constant of the mixture.
13–17 A gas mixture consists of 20 percent O 2 , 30 percent
N 2 , and 50 percent CO 2 on mass basis. Determine the volu-
metric analysis of the mixture and the apparent gas constant.P-v-TBehavior of Gas Mixtures
13–18C Is a mixture of ideal gases also an ideal gas? Give
an example.
13–19C Express Dalton’s law of additive pressures. Does this
law hold exactly for ideal-gas mixtures? How about nonideal-
gas mixtures?
13–20C Express Amagat’s law of additive volumes. Does this
law hold exactly for ideal-gas mixtures? How about nonideal-
gas mixtures?*Problems designated by a “C” are concept questions, and students
are encouraged to answer them all. Problems designated by an “E”
are in English units, and the SI users can ignore them. Problems
with a CD-EES icon are solved using EES, and complete solutions
together with parametric studies are included on the enclosed DVD.
Problems with a computer-EES icon are comprehensive in nature,
and are intended to be solved with a computer, preferably using the
EES software that accompanies this text.cen84959_ch13.qxd 4/6/05 9:35 AM Page 709