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Vapor/Liquid Vapor/Liquid EquilibriumEquilibrium

Energy Energy BalancesBalances

Multiphase Multiphase SystemsSystems

Nonreactive Nonreactive ProcessesProcesses

$600

How can you tell How can you tell which of two which of two

components is more components is more volatile?volatile?

What can you say about the What can you say about the bubble point and dew point bubble point and dew point temperatures of a mixture temperatures of a mixture of two components A and B of two components A and B (T(T⁰⁰b,Ab,A < T < T⁰⁰b,Bb,B)? What about )? What about

the compositions of the first the compositions of the first bubble and last drop of bubble and last drop of

mixture?mixture?

Explain why a soda can Explain why a soda can fizzes when it is fizzes when it is

openedopened

Draw the temperature plot Draw the temperature plot for heating pure for heating pure

cyclohexane from 20 C to cyclohexane from 20 C to 100 C at a pressure of 1 100 C at a pressure of 1

atm. State what is atm. State what is happening in each region of happening in each region of

the curve.the curve.

Write the equations to solve Write the equations to solve for the temperature and for the temperature and

composition of a liquid in composition of a liquid in equilibrium with a vapor that equilibrium with a vapor that is 30 mole% acetone-70 moleis 30 mole% acetone-70 mole% ethanol at 1 atm. Is this a % ethanol at 1 atm. Is this a

bubble-point or dew-point bubble-point or dew-point calculation? List vapor calculation? List vapor

pressures as a variable and pressures as a variable and state where you would find state where you would find

them.them.

What can you say What can you say about the enthalpy of a about the enthalpy of a system of air at 600 system of air at 600 ⁰⁰F F and 1 atm? The value and 1 atm? The value given in Table B.9 is given in Table B.9 is

3719 BTU/lbmol3719 BTU/lbmol

Cancel the terms of the energy Cancel the terms of the energy balance of the following balance of the following system and explain if the system and explain if the

remaining terms are positive remaining terms are positive or negativeor negative

IsothermalIsothermal

CondenserCondensermm1 1 kg Hkg H22O O

(v)/hr(v)/hr

P = 20 barP = 20 bar

T = 250 CT = 250 C

mm2 2 kg Hkg H22O O (v)/hr(v)/hr

P = 40 bar, P = 40 bar, sat’dsat’dmm3 3 kg Hkg H22O O (l)/hr(l)/hr

Complete the following table Complete the following table for waterfor water

State T (°C) P (bar) V (m3/kg)

U (kJ/kg)

Table

Vapor 50 Sat’d

Liquid 94 1

Vapor Sat’d 0.538

450 40

One thousand kilograms per hour One thousand kilograms per hour of steam drives a turbine. The of steam drives a turbine. The

steam enters the turbine at 60 bar steam enters the turbine at 60 bar and 450C. The turbine delivers and 450C. The turbine delivers

shaft work at a rate of 70 kW and shaft work at a rate of 70 kW and the heat loss is 20 kW. Calculate the heat loss is 20 kW. Calculate the final temperature of the steam the final temperature of the steam

if the final pressure is 0.5 bar.if the final pressure is 0.5 bar.

If a pump is 70 % efficient, how If a pump is 70 % efficient, how many kW are necessary to pump many kW are necessary to pump water flowing at 10 kg/s from a water flowing at 10 kg/s from a lake at 1 bar to an outlet 75 m lake at 1 bar to an outlet 75 m above the lake at 5 bar, if the above the lake at 5 bar, if the

outlet pipe has a 4 cm ID?outlet pipe has a 4 cm ID?

Define a colligative Define a colligative solution property? solution property? Name 3 of them.Name 3 of them.

Without using your Without using your book, what is the book, what is the

definition of bubble-definition of bubble-point and dew-point point and dew-point temperatures? What temperatures? What assumptions must be assumptions must be

made to apply Raoult’s made to apply Raoult’s or Henry’s Laws?or Henry’s Laws?

What is the dew point and composition of a What is the dew point and composition of a mixture of 70% 1-propanol with the rest 1-mixture of 70% 1-propanol with the rest 1-

pentanol in the vapor phase? pentanol in the vapor phase?

600

1000

1400

1800

2200

2600

3000

0 0.2 0.4 0.6 0.8 1

P (m

mH

g)

mole fraction 1-propanol

Pxy diagram at 135 ⁰C for 1-propanol and 1-pentanol mixture

Given the following Txy diagram for styrene Given the following Txy diagram for styrene in toluene at 1000 mm Hg, if a mixture with in toluene at 1000 mm Hg, if a mixture with 40 mole% of styrene is fed to an evaporator 40 mole% of styrene is fed to an evaporator what is the bubble-point temperature and what is the bubble-point temperature and

the equilibrium vapor composition?the equilibrium vapor composition?

110

120

130

140

150

160

0 0.2 0.4 0.6 0.8 1

T (⁰

C)

mole fraction styrene

Txy diagram at 1000 mmHg for styrene-toluene mixture

A gas containing OA gas containing O22 is in is in equilibrium with liquid water equilibrium with liquid water containing a small amount of containing a small amount of OO22 at 30C and 3 atm. Would at 30C and 3 atm. Would

you use Raoult’s Law or you use Raoult’s Law or Henry’s Law to estimate the Henry’s Law to estimate the

relationship betweenrelationship between

a.a.xxO2O2 and p and pO2O2

b.b. xxH2OH2O and p and pH2OH2O

and why?and why?

If HCN is taken from If HCN is taken from 25°C to 100°C, both 25°C to 100°C, both

states at 1 atm, but was states at 1 atm, but was carried out in such a way carried out in such a way that the pressure varied that the pressure varied during the heating, can during the heating, can

you still use Cyou still use Cpp to to calculate the specific calculate the specific

enthalpy and why?enthalpy and why?

Estimate the heat Estimate the heat capacity of solid CaCOcapacity of solid CaCO33

using Kopp’s Ruleusing Kopp’s Rule

Calculate the specific Calculate the specific enthalpies of the enthalpies of the

following processes:following processes:

a.a.NN22 (25°C to 700°C) (25°C to 700°C)

b.b.HH22 (800°F to 225°F) (800°F to 225°F)

Draw the process path of Draw the process path of n-pentane going from a n-pentane going from a solid at -150°C and 0.5 solid at -150°C and 0.5 atm to a vapor at 100°C atm to a vapor at 100°C and 4.0 atm. List where and 4.0 atm. List where

you would find the you would find the information to calculate information to calculate

ΔΔH for each step, but H for each step, but don’t calculate any of don’t calculate any of

them.them.

Suppose the formula Suppose the formula

was used to calculate the specific was used to calculate the specific enthalpy change for a change in enthalpy change for a change in

temperature and pressure fortemperature and pressure for

a.a. An ideal gasAn ideal gas

b.b.A highly nonideal gasA highly nonideal gas

c.c. A liquidA liquid

For which situation is the formula For which situation is the formula exact and which would have error?exact and which would have error?

2

1

)(ˆT

T

p dTTCH