Hydrogen gas is used in a process to manufacture a sheet material of 6-mm thickness. At the end of the process, H2 remains in solution in the material with a uniform concentration of 320kmol/m3. To remove H2 from the material, both surfaces of the sheet are exposed to an airstream at 500K and a total pressure of 3atm. Due to contamination, the hydrogen partial pressure is 0.1atm in the airstream, which provides a convection mass transfer coefficient of 1.5m/h. The mass diffusivity and solubility of hydrogen (A) in the sheet material (B) are DAB=2.6108m2/s and SAB=160kmol/m3atm, respectively. (a) If the sheet material is left exposed to the airstream for a long time, determine the final content of hydrogen in the material (kg/m3). (b) Identify and evaluate the parameter that can be used to determine whether the transient mass diffusion process in the sheet can be assumed to be characterized by a uniform concentration at any time during the process. Hint: This situation is analogous to that used to determine the validity of the lumped-capacitance method for a transient heat transfer analysis. (c) Determine the time required to reduce the hydrogen mass density at the center of the sheet to twice the limiting value calculated in part (a)