A 500 lbmol mixture of 48.8 mol% A and 51.2 mol% B with a relative volatility A,B

Question:

A 500 lbmol mixture of 48.8 mol% A and 51.2 mol% B with a relative volatility αA,B of 2.0 is to be separated in a batch rectifier consisting of a total condenser, a column with seven theoretical stages, and a partial reboiler. The reflux ratio is to be varied so as to maintain the distillation composition constant at 95 mol% A. The column can operate satisfactorily with a molar vapor boilup rate of 213.5 lbmol/h. The rectification is to be stopped when the mole fraction of A in the still drops to 0.192. Determine:

(a) The time required for rectification, and

(b) The total amount of distillate produced.