1. Separation of Helium by Diffusion Pyrex glass is virtually impermeable to all gases but Helium. Because of this, a Pyrex glass tube is seen as a means of separating He from natural gas. The closest competitor to He in diffusion through the glass is H2, but the ratio of the diffusivities of He to Hz in Pyrex is: Dne/DH2 = 25. For this problem, let A = He. MWHe = 4 g/mol. (a) Prove that rNA = const. in two ways: (i.) by shell balance, and (ii.) by the application of Egn. 19.1-10: -(. Na) + R : a = 1,2,3,..., N using the appropriate coordinates/geometry. Assuming movement in r- direction only, steady state and no reaction. at NAT NAIRE = -(v. Na) + Ra ; a = 1,2,3,...,N at (b) Determine the molar concentration profile of He (species A), assuming it remains dilute within the glass. (c) Under steady-state conditions at 293 K, the diffusivity is 2 x 10-8 cm/s and the partial pressures of He at the inner and outer surfaces of the Pyrex tube are 1.5 bar and 1 bar, respectively. If the wall of the tubing is 3 mm, and the inner diameter is 1 cm, determine the molar and mass loss rates through a total length of 20 m. Note: in reality, this would be a tube array, likely with - 50 tubes of 40 cm length