Problem 1 A sheet of BCC iron 1 mm thick was exposed to a carburizing gas atmosphere on one side and a decarburizing atmosphere on the other side at 725°C. After having reached steady state, the iron was quickly cooled to room temperature. The carbon concentrations at the two surfaces of the sheet were determined to be 0.012 and 0.0075 wt%. Compute the diffusion coefficient if the diffusion flux is 1.4 x 108 kg/m2-s. Hint: Use Equation 4.9(Text Book) to convert the concentrations from weight percent to kilograms of carbon per cubic meter of iron.

Problem 3. Phosphorus is diffused into a thick slice of silicon with no previous phosphorus in it at a temperature of 1100°C. If the surface concentration of the phosphorus is 1 x 10 atoms/cm and its concentration at 1 µm is 1 x 105 atoms/cm, how long must be the diffusion time? D = 3.0 x 10 cm?/s for P diffusing in Si at 1100°C.

A thin plastic membrane is used to separate helium from a current.gaseous. Under steady-state conditions, a concentration of helium in the membrane is known to be 0.02 and 0.005 kmol/m³ on the inner and outer surfaces, respectively. If the membrane has a thickness of 1 mm and the coefficient ofbinary diffusion of helium to plastic is 10^(-9) m²/ s, what is the value of the flow diffusive?

What mass of NaCl must be dissolved in 65.0 g of water to lower the freezing point of water by 7.5°C? The freezing point depression constant (Kf) for water is 1.86°C/m. Assume van’t Hoff factor for NaCl is 1.87. (Molar mass of NaCl = 58.5 g)