Mass Transfer Example
Question:

Think of the last time that you washed the dishes. You placed your first greasy plate into the water, and
the dishwater got a thin film of oil on the top of it, didn’t it? Find the flux, J, of oil droplets through the
water to the top surface.
The sink is 18 cm deep, and the concentration of oil on the plate is 0.1
mol/cm^{3}. Assume that there is no oil at the top of the sink
yet. 
Answer:
To solve this problem, we will need to apply the mass transfer equation we just learned.
J_{ }= D_{ }* D
C/D
x
where: D = 7 x 10^{7}cm^{2}/s
D
C = concentration at the top of the sink – the concentration of oil on the
plate.
The concentration at the top of the sink =
0
The concentration of oil on the plate = 0.1
mol/cm^{3}
D
C = 0 – 0.1 = 0.1 mol/cm^{3}
D
x = the depth of the sink = 18 cm
Since we know all of the numbers needed, we can calculate the flux.
J_{ }= D_{ }* D
C/D
x
J = (7 x 10^{7} cm^{2}/s) * (0.1 mol/cm^{3}) / (18 cm)
J = 4 x 10^{4} mol /
(cm^{2}s)
Good Job!
Return to Fick's Law
Return to Mass Transfer
[Introduction 
Kinetics 
Heat Transfer 
Mass Transfer 
Bibliography]
This project was funded in part by the National Science Foundation and
is advised by Dr. Masel and
Dr. Blowers at the
University of Illinois.