D8. A perfectly mixed membrane module is used to concentrate helium in retentate. Feed is 5.0 vol% helium and 95.0 vol% hydrogen at 5.0 atm. Membrane is natural rubber of the type used by Nakagawa (Table 18-2), and operation is at 25.0C. The active por- tion of membrane is 1.0 micron thick. Permeate pressure is 1.0 atm. Assume gases are ideal. b of == a. If pHe y b. If 0 = 0.75, what are pHe 0.025, what are cut 0 and y,He? and y,He? c. If yTHe = 0.06, what are cut 0 and pHe ? noted. For part a, what membrane area is required for a feed of 100.0 m (STP)/h?