1) Consider a two-component mixture (A & B) in vapor-liquid equilibrium.
Which of the following must be true?
1. μA, liq = μA, vap
2. xA = yA
3. vaporization & condensation have stopped
A) Only 1
B) 1 and 2
C) 2 and 3
D) 1, 2, and 3
yA, yB
Pvap, Tvap
xA, xB
Pliq, Tliq
2) The concentration of A is different in two immiscible liquids. What
determines the direction of mass transfer of component A?
A)
B)
C)
D)
E)
concentration
Pressure
Solubility
Energy
other
A in B
A in C
3) What is the driving force for component A to move from liquid to vapor to reach
equilibrium?
A) pressure
B) entropy
C) enthalpy
D) concentration
E) Gibbs free energy
vapor
yA
liquid
xA
4) Phases a and b each contain component A. The two phases are not in
equilibrium. The direction of mass transport of component A is
________.
A) from a to b
B) from b to a
C) cannot tell from this information
D) no mass transfer occurs
a
CA=0.001 mol/L
b
CA=0.020 mol/L
1) Air containing ammonia enters an absorption column. Water is used as
the absorbent. What happens when these two fluids are first brought into
contact?
A) ammonia dissolves in H2O
B) water transfers to air/NH3
C) no transfer
D) both A & B
Air +
Ammonia
Water
Liquid
Gas
2)
3) Two identical flasks are connected by a tube. Flask 1 contains water at
40°C. Flask 2 contains 50% more water at 35°C. As the system approaches
equilibrium, _______________.
A) water moves from 1 to 2
B) water moves from 2 to 1
C) no change occurs
1
2
H2O
40°C
H2O
35°C
4) Two identical flasks are connected by a tube. Flask 1 contains water at
40°C. Flask 2 contains 50% more water at 40°C. As the system approaches
equilibrium, _______________.
A) water moves from 1 to 2
B) water moves from 2 to 1
C) no change occurs
1
2
H2O
40°C
H2O
40°C
1) A liquid mixture containing species A and B is boiled by increasing the
temperature at constant pressure. The saturation pressure is greater for A
than for B. What happens over time?
A)
B)
C)
D)
xA increases and yA increases
xA increases and yA decreases
xA decreases and yA decreases
xA decreases and yA increases
2) An ideal liquid solution that is 30% A, 30% B, and 40% C is heated at a
constant pressure until 80% of the original liquid has evaporated. Which
component would you expect to have completely evaporated at that point?
PAsat > PBsat > PCsat
A)
B)
C)
D)
A
B
C
none of them
3) A liquid mixture of 50 mol% n-pentane (Psat = 5.7 bar) and 50 mol% nheptane (Psat = 1 bar) is at high pressure. The mixture is partially vaporized by
isothermally lowering the pressure to just below 3 bar. Which statement is
correct?
A)
B)
C)
D)
n-heptane is enriched in the gas phase
n-pentane is enriched in the gas phase
the gas phase has a 50/50 composition
no vapor forms