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Mass Transfer
Mass Transfer Operations
GATE 2012
Hard

An equimolar mixture of A and B (A being more volatile) is flash distilled continuously at a feed rate of 100 kmol/h, such that the liquid product contains 40 mol% of A. If the relative volatility is 6, then the vapor product, in kmol/h, is

  • A10
  • B20
  • 25
  • D45

Explanation

xA=0.4, α=6: y*A=αxA/(1+(α−1)xA)=6×0.4/(1+5×0.4)=2.4/3=0.8. Overall balance: F·zF=V·y+L·x, F=100, zF=0.5: 100×0.5=0.8V+0.4(100−V) ⟹ 50=0.8V+40−0.4V ⟹ 10=0.4V ⟹ V=25 kmol/h.

Source: GATE CH 2012 (2012)

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