HW03, ChE120C, Due Fri. May 24, 2013

1. Cussler 6.14

2. Askill 1970 found that self-diffusivities for many fcc and bcc metals follow D = D0exp[-ATm/RT] where Tm is the melting temperature in Kelvin, A = 38 cal/mol/K, and D0 = 1.0cm2/s. Will activation energy for solute diffusivity also scale with melting temperature of the surrounding metal? Calculate the diffusivity of Na in bcc Na at 25oC. Calculate the diffusivity of Mo in bcc Mo at 25oC.

3. Revisit the falling film and compute the mass transfer coefficient for transfer of A from the surface of the water film where cA = cAs to the rest of the liquid. Assume the penetration depth is very small over the entire length of the falling film. You may need Mathematica here.

4. Cussler 8.2

5. In an apparatus used for studying SO2 absorption by water, the overall mass transfer coefficient was KP = 300 mol SO2/(m

2 h atm). Assuming that 40% of the resistance to mass transfer is in the gas phase, calculate the overall mass transfer coefficient based on the liquid concentration. The system temperature is 30oC and the pressure is 1atm. Henry’s law for SO2 is PSO2 = (25atm) xSO2.

Cussler 6.14

8.2