1) A 5mm thick sheet of palladium with a cross sectional area of 0.2m^2 is used as a steady-state diffusion membrane in order to purify H2.The H2 concentration on the high pressure side of the sheet (i.e., the impure H2) is 1.5kg/m3 and that at the low pressure side is 0.3kg/m3. The diffusion coefficient for H2 in palladium is 1x10^-8m2/s. Assume a linear concentration profile within the plate. Calculate the mass of H2 being purified per hour.
2) If a (carburizing) carbon-containing gas diffuses under the surface of a steel shaft, the concentration of carbon under the surface will increase with time as the process proceeds. The steel shaft initially has a carbon content of 0.2wt%. Calculate the time, in minutes, necessary to increase the carbon content to 0.4wt%, at a distance of ½mm below the surface. The temperature is 1700°F. The carbon content at the surface is 0.892wt%. The diffusion coefficient at 1700°F is 1.28×10^-11m2/s.