Consider loss of ethanol vapor by diffusion from a half-filled open test tube. At what point in the diffusion path will the contribution of the bulk flow term to the molar flux be maximum? (Allocation time: 2 min)

A sheet of Fe 1.0 mm thick is exposed to an oxidizing gas on one side and a deoxidizing gas on the other at 725°C. After reaching steady state, the Fe membrane is exposed to room temperature, and the C concentrations at each side of the membrane are 0.012 and 0.075 wt%. Calculate the diffusion coefficient (m²/s) of C if the diffusion flux is 1.4×10^-8 kg/m².s. (Allocation time: 15 min)

In industries titanium is hardened through diffusion of carbon. The concentration of carbon at 1 mm into the surface of the titanium slab is 0.25 kg/m³ and at 3 mm the concentration is 0.68 kg/m³. The rate at which the carbon is entering into its surface is 1.27x10^-9 kg/m².s. Calculate the value of diffusion coefficient (m²/s) of carbon. (Allocation time: 15 min)