Mass Transfer Flashcards
What is the value of βπ½π, where π½π is the one-dimensional diffusive flux of species π?
a. 0
b. 1
c. β
a. 0
In a binary system, it is always true that π·π΄π΅ = π·π΅π΄?
Yes
f the temperature is increased, the gas-phase diffusivity will
a. increase
b. decrease
c. not change
a. increase
If the pressure is increased, the gas-phase diffusivity will
a. increase
b. decrease
c. not change
b. decrease
The relationship stating that the equilibrium mole fraction in a liquid of a weakly soluble species is
proportional to the partial pressure of that species in an adjacent gas is called
a. Raoultβs law
b. Henryβs law
c. the Davis-Sprenger rule
b. Henryβs law
[Equimolar Counter Diffusion: Diagrams in 22b]
What do you think the concentration profiles for the two species will look like as a function of z (from z
= 0 to z = L/2)?
a. Profile A
b. Profile B
c. Profile C
a. Profile A
What does the fact that NB,z is approximately 0 imply about the convective flux term in Fickβs Law of
Diffusion equation?
a. It implies that the convective flux term is negligible
b. It implies that NA,z is also approximately 0
c. Nothing.
c. Nothing.
Which of the following statements is true about RA, the rate of molar production for a homogeneous
reaction at steady state?
a. It has no direction (is a scalar) and is the divergence of NA
b. It is directional, because it is dependent on the direction of the flux, NA
a. It has no direction (is a scalar) and is the divergence of NA
True or False? Diffusion coefficients for gases are often measures using Arnold Diffusion Cell.
True
If the Thiele modulus is large compared to unity, is the reaction-diffusion process
a. diffusion-limited (slow diffusion, fast reaction)?
b. reaction-limited (fast diffusion, slow reaction)?
c. indeterminant?
a. diffusion-limited (slow diffusion, fast reaction)?
[Example in 25a]
About how long will it take a chemotherapy drug to diffuse most of the way into a tissue?
a. Two hours
b. Two days
c. Two weeks
d. Two months
c. Two weeks
If a medium of depth π» has πΆπ΄ = πΆπ΄0 for all π§ at π‘ < 0, and then suddenly the boundary condition is
changed to πΆπ΄ = πΆπ΄π > πΆπ΄0 at π§= 0 for π‘ β₯0, then the flux of π΄ at π§ = 0, π‘ = 0 is
a. 0
b. β
c. π·π΄π΅(πΆπ΄π β πΆπ΄0)/π»
b. β
What is the ratio of convection and diffusion of the sweep gas π΅ in an Arnold diffusion cell?
a. 0
b. β
c. 1
d. β1
d. β1
In an Arnold diffusion cell, the evaporating Species A undergoes
a. diffusion only
b. convection only
c. both diffusion and convection
c. both diffusion and convection
In an Arnold diffusion cell, the sweep Species B undergoes
a. diffusion only
b. convection only
c. both diffusion and convection
c. both diffusion and convection
