Helium gas is stored at 293 K in a 3-m-outer-diameter spherical Container made of 3-cm-thi...

Helium gas is stored at 293 K in a 3-m-outer-diameter spherical Container made of 3-cm-thick Pyrex. The molar concentration of helium in the Pyrex is 0.00069 kmol/m3 at the inner surface and negligible at the outer surface. Determine the mass flow rate of helium by diffusion through the Pyrex Container. Answer: 2.87 × 10–15 kg/s