Chem. 303 Lab 3 Post Lab Questions 1. A mixed liquid sample contains 0.7 mol of

Question

Chem. 303 Lab 3 Post Lab Questions 1. A mixed liquid sample contains 0.7 mol of A which has a vapor pressure of 200 mmHg at 25°C and 0.3 mol of B which has a vapor pressure of 1200 mmlig at 25°C. Will this sample boil at 25°C? Why or why not? If it boils, what is the concentration of each substance in the vapor phase at equilibrium? Show all your work. 2 Why is the abdlity to separate 2 liquids by fractional distillation drastically reduced if heat is applied too rapidly to the distillation flask?

Explanation / Answer

1. No, the mixture won't boil at 250C. Since, at boiling point, the atmospheric pressure or the pressure of the surroundings become equal to the vapour pressure exerted by the mixture, here it can be seen as follows, that the vapour pressure of the mixture is less than the atmospheric pressure:

Total Pressure of mixture= mole fraction of A* VP of A + mole fraction of B* VP of B.

=0.7/(0.7+0.3) *200mm Hg + 0.3/(0.3+0.7) * 1200mm Hg.

= 500mm Hg.

And we know that the atmospheric pressure at 25 degrees is 760mm. Hence, the mixture won't boil.

2. If one rapidly supplies heat to the distillation flask in fractional distillation, then the vapourisation of both the liquids take place quickly with the plenty of heat supplied and then there remains very little chance for one to cool and condense the column going up before it hits the condenser.

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.