One hundred lbmol of benzene (B), monochlorobenzene (MCB), and o-dichlorobenzene (DCB) is distilled in a batch rectifier that has a total condenser, a column with 10 theoretical stages, and a stillpot. Following establishment of total reflux, the first operation step begins at a boilup rate of 200 lbmol/h and a reflux ratio of 3. At the end of 0.60 h, the following conditions exist for the top three stages in the column:

In addition, still-pot and condenser holdups at 0.6 h are 66.4 and 0.1113 lbmol, respectively. For benzene, use the preceding data with (13-36) and (13-39) to estimate the liquid-phase mole fraction of benzene leaving Stage 2 at 0.61 h by using the explicit-Euler method with a Dt of 0.01 h. If the result is unreasonable, explain why, with respect to stability and stiffness considerations.

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Temperature, F V, lbmol/h L, Ibmol/h M, lbmol Top Stage 267.7 206.1 157.5 Vapor Mole Fractions: B MCB DCB Liquid Mole Fractions: B MCB DCB 0.01092 0.0994 0.9006 0.0000 0.0276 0.9724 0.0000 Stage 2 271.2 209.0 158.0 0.01088 0.0449 0.9551 0.0000 0.0121 0.9879 0.0000 Stage 3 272.5 209.5 158.1 0.01087 0.0331 0.9669 0.0000 0.00884 0.99104 0.00012