Project ForgeIn a batch (Rayleigh/differential) distillation of an equimolar benzene-toluene mixture at atmospheric pressure, the mole fraction of benzene in the distillate collected after 10 minutes is 0.6. The process continues for another 10 minutes. The mole fraction of benzene in the TOTAL distillate collected after 20 minutes of operation is
- less than 0.6
- Bexactly equal to 0.6
- Cexactly equal to 0.7
- Dgreater than 0.7
Explanation
In differential distillation, the still's liquid progressively depletes of the more volatile component, so the instantaneous distillate composition continuously decreases over time. The second 10-minute increment's distillate composition is necessarily lower than the first increment's average (0.6), so the new cumulative average over 20 minutes must be less than 0.6.
Source: GATE CH 2020 (2020)
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