- Example 5: [One-way diffusion] Methane gas is diffusing in a straight tube 0.1m long containing at 298K and a total pressure of 1.01325105Pa. The partial pressure of CH4 is 1.400104Pa at one end and 1.333103Pa at the other end. Helium is insoluble in one boundary, and hence is nondiffusing or stagnant. The diffusivity is 0.675cm2/sec at 25C. Calculate the flux of methane at steady state. (Sol.: NA=3.74106kgmolA/s2m2 ) - Example 6 : [One-way diffusion] A sphere of naphthalene having a radius of 2.0mm is suspended in a large volume of still air at 318K and 1.101325105Pa(1atm). The diffusivity of the naphthalene at 318K is 6.92106m2/s. At surface of naphthalene, pA1=0.555mmHg. Calculate the rate of evaporation of naphthalene from the surface. (Sol.: NA1=9.68108 kgmolA/s.m2)