A batch distillation system with a still pot and one equilibrium stage (two equilibrium contacts total) distills a feed that is \(10.0 \mathrm{~mol} \%\) water and \(90.0 \mathrm{~mol} \% \mathrm{n}\)-butanol (see Table \(8-5\) for VLE data). \(\mathrm{p}=1.0 \mathrm{~atm}\). The charge is \(4.0 \mathrm{kmoles}\). The final still concentration is \(2.0 \mathrm{~mol} \%\) water. The system has a total condenser, and the reflux is a saturated liquid. \(\mathrm{L} / \mathrm{D}=\) \(1 / 2\). Find the final number of moles in the still pot and the average concentration of distillate.

Table 8-5

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TABLE 8-5. VLE data for water and n-butanol at 1.0 atm mol% water Liquid Vapor TC Liquid Vapor TC 0.0 0.0 117.0 57.3 75.0 92.8 3.9 26.7 111.5 97.5 75.2 92.7 4.7 29.9 110.6 98.0 75.6 93.0 5.5 32.3 109.6 98.2 75.8 92.8 7.0 35.2 108.8 98.5 77.5 93.4 25.7 62.9 97.9 98.6 78.4 93.4 27.5 64.1 97.2 98.8 80.8 93.7 29.2 65.5 96.7 99.2 84.3 95.4 30.5 66.2 96.3 99.4 88.4 96.8 49.6 73.6 93.5 99.7 92.9 98.3 50.6 74.0 93.4 99.8 95.1 98.4 55.2 75.0 92.9 99.9 98.1 99.4 56.4 75.2 92.9 100.0 100.0 100.0 57.1 74.8 92.9