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Mass Transfer
Mass Transfer Operations
GATE 2013
Hard

A liquid having the composition found in the first part of the linked answer question above (xA=1/(1+√αAB) with αAB=2.5), is flash distilled at a steady state to a final liquid mole fraction of 0.25. If αAB is 2.5, the fraction of the feed vaporized is

  • A0.08
  • B0.20
  • 0.67
  • D0.74

Explanation

Feed composition zF=1/(1+√2.5)=1/2.5811=0.3874. Final liquid x=0.25; equilibrium vapor y*=2.5×0.25/(1+1.5×0.25)=0.625/1.375=0.4545. Overall balance with q=V/F: zF=q·y*+(1−q)·x ⟹ 0.3874=0.4545q+0.25(1−q) ⟹ 0.1374=0.2045q ⟹ q≈0.67.

Source: GATE CH 2013 (2013)

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