Chemistry · The vapour pressure of solutions and Raoult's Law - Ideal and non-ideal solutions, vapour pressure composition, plots for ideal and non-ideal solutions

At , the vapour pressure of toluene is 400 torr and that of lene is 150 torr. Wh

At \( 90^{\circ} \mathrm{C} \), the vapour pressure of toluene is 400 torr and that of \( \sigma-x y \) lene is 150 torr. What is the composition of the liquid mixture the boils at \( 90^{\circ} \mathrm{C}, \) when the pressure is 0.50 atm? What is the composition of vapour produced?

  • A. Toluene 8 mol\%, Toluene=3.2 mol\%
  • B. Toluene 15mol\%, Toluene=36 mol\%
  • C. Toluene 85 mol\%, Toluene=64 mol\%
  • D. Toluene 92 mol\%, Toluene \( =96.8 \mathrm{mol\%} \)

Step-by-step solution

Use Raoult's law for ideal solution. Let x = mole fraction of toluene in liquid. Total pressure = x*400 + (1-x)*150 = 380 torr (0.50 atm = 380 torr). Solving gives x = 0.92, so liquid is 92 mol% toluene. Vapour composition: partial pressure of toluene = 0.92*400 = 368 torr, so mole fraction in vapour = 368/380 = 0.968 = 96.8 mol%.
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