• A continuous rectifying column handles a mixture consisting of 40 per cent of benzene by mass and 60 per cent of toluene at the rate of 4 kg/s, and separates it into a product containing 97 per cent of benzene and a liquid containing 98 per cent toluene. The feed is liquid at its boiling-point. (a) Calculate the mass flows of distillate and waste liquor. (b) If a reflux ratio of 3.5 is employed, how many plates are required in the rectifying part of the column? (c) What is the actual number of plates if the plate-efficiency is 60 per cent? Mole fraction of benzene in liquid 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Mole fraction of benzene in vapour 0.22 0.38 0.51 0.63 0.7 0.78 0.85 0.91 0.96