Gas-Liquid Equilibria Flashcards
What are the 4 things that define an ideal liquid
- Mutual solubility
- No chemical reactions occur upon mixing
- The molecular diameters of the components are the same
- The intermolecular forces of attraction and repulsion are the same between unlike as those between like molecules
With the 4 assumptions about ideal solutions, what 2 practical results can be reached
- There is no heating effect when the components are mixed
- The volume of the ideal solution equals the volume of the components would occupy alone at the same P and T
Real gas-liquid solution approached ideal-solution behavior at low______
pressures
What does Raoult’s equation state
The partial pressure of a pure component in the gas phase is equal to the mole fraction of that component in the liquid phase times it vapor pressure at the temperature of interest
Pj = XjPvj (T)
is Raoult’s equation valid for ideal and non-ideal solutions
No, it is only valid for ideal solutions
What is Daltons Equation used for
Used to calculate the partial pressure of a component of an ideal GAS mixture
Pj = YjP
where do we find the vapor pressure of a substance
Figure 2-7 and 2-8
What are the 3 major limitations for the ideal solution equations(Xj and Yj)
- Raoult’s equation - gas and liquid are not in equilibrium
- Daltons equation - only considers gas. P < 100 psia and at high temp
- A pure compound does not have a vapor pressure at T > Tc. - calculations are limited at temps below Tc
What can we call the K-Factor? Is it constant?
equilibrium ratio(G/L), vaporization equilibrium constant, equilibrium vapor liquid distribution ratio, distribution coefficient.
It is not constant, it changes with P, T, composition and type of mixture
If we are calculating bubble point pressure and when we do sum of zjkj and its less than 1, should we increase our pressure guess or decrease it
decrease the pressure guess
the ______ pressure, the larger Kj = yj / xj
i.e., more gas and less liquid in equilibrium
lower
If we are calculating bubble point pressure and when we do sum of zjkj and its greater than 1, should we increase our pressure guess or decrease it
increase the pressure guess
describe differential vaporization
a process in which the gas is removed from contact with the liquid by steps as the gas is formed. Each increment of gas removed changes the composition of the liquid
What are the two cases for differential vaporization
- Initial conditions and the final pressure are given to calculate the number of moles to be vaporized
- The initial conditions and the number of moles to be vaporized are given to calculate the final pressure Pr
The key assumption used in the differential vaporization calculations
(Cases #1 & #2) is that _____ remains constant in the pressure interval.
Kj
The error caused by Kj-factors can be minimized by using a much
________ ________ change in each step in a finer stepwise manner.
smaller pressure
A ___________ vaporization process is really a series of
___________ vaporizations, except that the gas is removed at the end of each
flash test in this process. In a typical ___________ vaporization test, the released
gas is always kept in contact with the remaining liquid phase at all times.
differential
flash
flash
