1. A packed column is to be designed to absorb benzene vapor from air by contacting it with a hydrocarbon oil at 25 C and 760 mmHg. The partial pressure of benzene will be reduced from 6 mmHg to 0.5 mmHg. The entering hydrocarbon oil is benzene-free. Calculate: a. The minimum value of L/G ratio, b. The number of the over-all gas transfer units needed, for an operating L/G ratio which is 1.25 times the minimum L/G ratio. Equilibrium relationship at 25 C and 760 mmHg is y*= 0.12 x, where y* and x | are the mole fractions of benzene in gas and liquid respectively.