ChE 123: Introduction to Vapor/Liquid Equilibrium

Question 1

Microscopically, the conditions in equilibrium are?

Answer 1

not static

Question 2

still holds priority over Duhem’s Theorem

Answer 2

gibb’s phase rule

Question 3

this is where two substances are found at the same pressure

Answer 3

mechanical equilibrium

Question 4

this states that the partial pressure of the species in vapor phase is directly proportional to its
liquid-phase mole fraction

Answer 4

Henry’s Law

Question 5

this states that the partial pressure of each component of an ideal mixture of liquids is equal to the vapor pressure of the pure component multiply by its mole fraction in liquid phase

Answer 5

raoult’s law

Question 6

Different unit operations such as ______________ and ________________ involve different phases to come
into contact.

Answer 6

distillation ; gas absorption

Question 7

It states that: “For any closed system formed initially from given masses of prescribed chemical species, the equilibrium state is completely determined when any two independent variables are fixed.”

Answer 7

Duhem’s Theorem

Question 8

rate of evaporation = rate of condensation

Answer 8

dynamic equilibrium

Question 9

this is where no reaction takes place in the system and chemical composition does not vary over time

Answer 9

chemical equilibrium

Question 10

this is another rule similar to the phase rule but is applied to closed systems at equilibrium when both extensive and intensive states are fixed

Answer 10

duhem’s theorem

Question 11

it is the point (T or P) where the first drop of a liquid mixture starts to vaporize

Answer 11

bubble point

Question 12

the number of intensive variables that must be defined is still dictated by the

Answer 12

gibb’s phase rule

Question 13

this type of equilibrium is where microscopically, the conditions are not static

Answer 13

dynamic equilibrium

Question 14

this is where two substances are found at the same temperature

Answer 14

thermal equilibrium

Question 15

It is important to determine the equilibrium T, P, and phase composition for these phases since
their departure from equilibrium conditions allow?

Answer 15

mass transfer

Question 16

a method to determine the number of independent variables/degrees of freedom (F) for a system at equilibrium

Answer 16

gibb’s phase rule

Question 17

Different types of calculations will be:

Answer 17

a. Bubble P
b. Bubble T
c. Dew P
d. Dew T

Question 18

it is the difference between the total number of intensive variables
and the number of independent equations

Answer 18

degrees of freedom

Question 19

Assumptions & Limitations of Raoult’s Law

Answer 19

a. the vapor phase is in ideal gas
- can only be applied to low to moderate pressures
b. the liquid phase is an ideal solution
- The molecular species are not too different in size and of same chemical nature

Question 20

The goal in VLE is to calculate the?

Answer 20

a. T
b. P
c. compositions of phases in equilibrium

Question 21

the amount of vapor and liquid remain constant over time

Answer 21

dynamic equilibrium

Question 22

it is a static condition in which no changes in the macroscopic properties of a system with time

Answer 22

equilibrium

Question 23

this is equal to the mole fraction in vapor phase multiplied by the total pressure

Answer 23

partial pressure of component

Question 24

it is also related to the tendency of the particles to escape from liquid

Answer 24

vapor pressure

Question 25

the evaporation and condensation are continuously occurring at same rates

Answer 25

dynamic equilibrium

Question 26

Vapor Pressure ______________ with temperature

Answer 26

increases

Question 27

this also means that the amount of gas dissolved in a liquid is directly proportional to the partial pressure of the gas above the liquid

Answer 27

Henry's Law

Question 28

This tells us the number of intensive properties we must define first before we can define the whole thermodynamic system

Answer 28

degrees of freedom

Question 29

this is the pressure exerted by the vapor in equilibrium with its condensed phase (solid or liquid) in a closed container

Answer 29

vapor pressure

Question 30

this is used for dilute species at low pressures

Answer 30

Henry's Law

Question 31

this represents the number of components

Answer 31

N

Question 32

The simple models for the calculations of T, P, and compositions of phases in equilibrium are

Answer 32

a. Raoult's Law b. Henry's Law

Question 33

this represents the number of phase

Answer 33

pi

Question 34

it is the point (T or P) where the first drop of a vapor mixture starts to condense

Answer 34

dew point