2.3. Diffusion Across the Interface

Try these first

1. 1.

   What is the role of the interface in mass transfer?

   Hint

   Think about where two phases meet.

2. 2.

   Define mass transfer coefficient.

   Hint

   Consider what happens when different materials interact.

3. 3.

   What defines an interface in mass transfer?

   • A solid boundary
   • A meeting of two phases
   • An imaginary line

   Hint

   Think of a beaker with water and air.

4. 4.

   True or False: The concentration gradient remains the same at all depths in a beaker of water.

   • True
   • False

   Hint

   Consider how density changes with depth.

5. 5.

   Given a concentration of a substance in the water at 100 mg/L and a corresponding air equilibrium concentration of 2 mg/L, calculate the mass transfer coefficient if the flux is was found to be 10 mol/m^2/s.

   Hint

   Make sure to use the steady state conditions properly.

6. 6.

   A lake has turbulent conditions on the surface that enhances mass transfer. If you find that the concentration gradient between air and water is 1.5 mg/L/m, how would the increased turbulence affect the mass transfer calculations?

   Hint

   Think about the physical impact of turbulence on fluid mixing.