Raoult's law

Question 1

What is Raoult’s Law?

Answer 1

Raoult’s Law states that the saturated vapour pressure of each solvent in a mixture is equal to the product of the vapour pressure of the pure component and its mole fraction

Question 2

What is the mole fraction of a solvent given by?

Answer 2

Xsolvent = Na/(Na + Nb)

Where Na = number of moles of a
Where Nb = number of moles of b

Question 3

What is the mole fraction in vapour phase?

Answer 3

Ya = Pa/Pt

Where Pa = vapour pressure of substance A

Pt = vapour pressure of solution

Question 4

What is Raoult’s Law of Vapour Pressure Lowering?

Answer 4

It states that the vapour pressure lowering of a solvent is directly proportional to the mole fraction of the solute added.

∆P = Xsolute • P⁰solvent

Where P⁰ = vapour pressure in pure state (NOT p-raised to 0)

Question 5

What is the negative deviation from Raoult’s law?

Answer 5

Negative deviation from Raoult’s law occurs when the total vapour pressure of the solution is lower then the vapour pressure predicted by Raoult’s law.

Question 6

What is the positive deviation from Raoult’s law?

Answer 6

Positive deviation from Raoult’s law occurs when the total vapour pressure of the solution is higher than the vapour pressure predicted by Raoult’s law.