Diffusion - Practice Problems_Villanueva

A gas of CH4 and He is contained in a tube at 101.32 kPa pressure and 298 K. At one point the partial pressure of methane is 60.79 kPa and at a point 0.02 m distance away, the partial pressure of methane is 20.26 kPa. If the total pressure is constant throughout the tube, calculate the flux of CH4 at steady state for equimolar counterdiffusion.

The gas CO2 is diffusing at steady state through a tube 0.20 m long having a diameter of 0.01 m and containing N2 at 298 K. The total pressure is constant at 101.32 kPa. the partial pressure of CO2 is 456 mmHgat one end and 76 mmHG at the other end. The diffusivity is 1.67 E-05 m2/s at 298 K. Calculate the flux of CO2 in SI units for equimolar counterdiffusion.

Geankoplis 6.2-4 Diffusion of Methane Through Nondiffusing Helium

Geankoplis 6.2-8 Evaporation Losses of Water in Irrigation Ditch

Answer in lbm/day

A drop of liquid toluene is kept at a uniform temperature of 25.9C and is suspended in air by a fine wire. The initial radius r1=2.00 mm. The vapor pressure of toluene at 25.9 C is 3.84 kPa and the density of liquid toluene is 866 kg/m3.

Calculate the time in seconds for complete evaporation.

Diffusion of Ethanol (A) through water (B)

An ethanol-water solution in the form of a stagnant film 2.0 mm thick at 293 is in contact at one surface with an organic solvent in which ethanol is soluble and water is insoluble. At point 1, the concentration of ethanol is 16.8 wt% and the solution density is 972.8 kg/m3. At point 2, the concentration of ethanol is 6.8 wt% and the solution density is 988.1 kg/m3. The diffusivity of ethanol is 0.740 E-09 m2/s. Caclulate the steady-state flux.

Vaporizing A and Convective Mass Transfer

A large volume of pure gas B at 2 atm pressure is flowing over a surface from which pure A is vaporizing. The liquid A completely wets the surface, which is a blotting paper. Hence, the partial pressure of A at the surface is the vapor pressure of A at 298 K, which is 0.20 atm. The k'y has been estimated to be 6.78 E-05 kgmol/s m2 mol frac. Calculate the vaporization rate.

Mass Transfer from a Flat Plate

A large volume of pure water at 26.1 C is flowing parallel to a flat plate of solid benzoic acid, where L = 0.244 m in the direction of flow. The water velocity is 0.061 m/s. The solubility of benzoic acid in water is 0.02948 kg mol/m3. The diffusivity of benzoic acid is 1.245 E-09 m2/s. Calculate the flux.