A distillation unit consists of a partial reboiler, a column with seven equilibrium plates, and a total condenser. The feed is a 50 mol % mixture of benzene in toluene. It is desired to produce a distillate containing 96 mol% benzene, when operating at 101 kPa.
(a) With saturated-liquid feed fed to the fifth plate from the top, calculate:
(1) Minimum reflux ratio (L_R/D)_min; 

(2) The bottoms composition, using a reflux ratio (L_R/ D) of twice the minimum; and 

(3) Moles of product per 100 moles of feed. 

(b) Repeat part (a) for a saturated vapor fed to the fifth plate from the top.

(c) With saturated-vapor feed fed to the reboiler and a reflux ratio (L / V) of 0.9, calculate: 

(1) Bottoms composition, and 

(2) Moles of product per 100 moles of feed.