CHE 205
Vapor/Liquid
Equilibrium
Energy Balances
Multiphase
Systems
Nonreactive
Processes
$200
$200
$200
$200
$400
$400
$400
$400
$600
$600
$600
$600
$800
$800
$800
$800
$1000
$1000
$1000
$1000
How can you tell which
of two components is
more volatile?
What can you say about the
bubble point and dew point
temperatures of a mixture of two
components A and B (T⁰b,A <
T⁰b,B)? What about the
compositions of the first bubble
and last drop of mixture?
Explain why a soda can
fizzes when it is opened
Draw the temperature plot for
heating pure cyclohexane from 20
C to 100 C at a pressure of 1 atm.
State what is happening in each
region of the curve.
Write the equations to solve for the
temperature and composition of a
liquid in equilibrium with a vapor
that is 30 mole% acetone-70 mole%
ethanol at 1 atm. Is this a bubblepoint or dew-point calculation? List
vapor pressures as a variable and
state where you would find them.
What can you say about the
enthalpy of a system of air
at 600 ⁰F and 1 atm? The
value given in Table B.9 is
3719 BTU/lbmol
Cancel the terms of the energy balance
of the following system and explain if
the remaining terms are positive or
negative
m2 kg H2O (v)/hr
m1 kg H2O (v)/hr
Isothermal
P = 40 bar, sat’d
P = 20 bar
Condenser
m3 kg H2O (l)/hr
T = 250 C
Complete the following table for
water
State
T (°C)
P (bar)
Vapor
50
Sat’d
Liquid
94
1
Vapor
Sat’d
450
V
(m3/kg)
0.538
40
U
(kJ/kg)
Table
One thousand kilograms per hour of
steam drives a turbine. The steam enters
the turbine at 60 bar and 450C. The
turbine delivers shaft work at a rate of 70
kW and the heat loss is 20 kW. Calculate
the final temperature of the steam if the
final pressure is 0.5 bar.
If a pump is 70 % efficient, how many kW
are necessary to pump water flowing at 10
kg/s from a lake at 1 bar to an outlet 75 m
above the lake at 5 bar, if the outlet pipe
has a 4 cm ID?
Define a colligative
solution property? Name
3 of them.
Without using your book,
what is the definition of
bubble-point and dew-point
temperatures? What
assumptions must be made
to apply Raoult’s or Henry’s
Laws?
What is the dew point and composition of a mixture of
70% 1-propanol with the rest 1-pentanol in the vapor
phase?
Pxy diagram at 135 ⁰C for 1-propanol and 1pentanol mixture
3000
P (mmHg)
2600
2200
1800
1400
1000
600
0
0.2
0.4
0.6
mole fraction 1-propanol
0.8
1
Given the following Txy diagram for styrene in
toluene at 1000 mm Hg, if a mixture with 40 mole% of
styrene is fed to an evaporator what is the bubblepoint temperature and the equilibrium vapor
composition?
Txy diagram at 1000 mmHg for styrenetoluene mixture
160
T (⁰C)
150
140
130
120
110
0
0.2
0.4
0.6
mole fraction styrene
0.8
1
A gas containing O2 is in equilibrium
with liquid water containing a small
amount of O2 at 30C and 3 atm.
Would you use Raoult’s Law or
Henry’s Law to estimate the
relationship between
a. xO2 and pO2
b. xH2O and pH2O
and why?
If HCN is taken from 25°C to
100°C, both states at 1 atm, but
was carried out in such a way
that the pressure varied during
the heating, can you still use Cp
to calculate the specific
enthalpy and why?
Estimate the heat capacity of
solid CaCO3 using Kopp’s Rule
Calculate the specific
enthalpies of the following
processes:
a.N2 (25°C to 700°C)
b.H2 (800°F to 225°F)
Draw the process path of npentane going from a solid at 150°C and 0.5 atm to a vapor at
100°C and 4.0 atm. List where
you would find the information
to calculate ΔH for each step,
but don’t calculate any of them.
Suppose the formula
T2
Hˆ   C p (T )dT
T1
was used to calculate the specific enthalpy
change for a change in temperature and
pressure for
a. An ideal gas
b. A highly nonideal gas
c. A liquid
For which situation is the formula exact and
which would have error?