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GATE 2024 Chemical Engineering, Q18 · Thermodynamics

The correct answer is A, 1.0.

Question

Consider a vapour-liquid mixture of components A and B that obeys Raoult's law. The vapour pressure of A is half that of B. The vapour phase concentrations of A and B are 3mol/m33 mol/m³ and 6mol/m3,6 mol/m³, respectively. At equilibrium, the ratio of the liquid phase concentration of A to that of B is

  • A. 1.0
  • B. 0.5
  • C. 2.0
  • D. 1.5

Official answer: 1.0

Why

GATE 2024 official key: (A). yA=1/3,yB=2/3.y_{A}=1/3, y_{B}=2/3. Raoult's law: xA/xB=(yA/yB)×(PB∗/PA∗)=(1/2)×2=1.0.x_{A}/x_{B} = (y_{A}/y_{B}) \times (P_{B}*/P_{A}*) = (1/2) \times 2 = 1.0.

Explanation cross-checked for consistency. Final answer matches the official IIT answer key.

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