When two volatile liquids (x and y) are mixed, the solution process involves 1. breaking the intermolecular and attractions, and 2. forming new attractions.
complete this table describing how the relative strengths of these attractive forces affect vapor pressure and enthalpy of solution.
1. , , and are equal
2. is strongest
3. is weakest
raoult's law deviations & deltahsoln

1. X --- X, Y --- Y, and X --- Y are equal

delta H = 0 and Raoult's Deviation = 0

2. X --- Y is the strongest

delta H = - and Raoult's Deviation = negative

3. X --- Y is the weakest

delta H = + and Raoult's Deviation = positive

In mixing the two solutions, it will require energy to break the attraction of each solution and create a new attraction that produces energy.

If both are equal then there will be no heat released or received so that the delta H solution is 0, which indicates that the solution is ideal

Raoult's Law states that the magnitude of the vapor pressure of a solution is proportional to the mole fraction of the solvent and the vapor pressure of the pure solvent

So the vapor pressure of a component depends on the mole fraction of that component in the solution

Can be formulated:

P = solution vapor pressure

X = mole fraction

Po = vapor pressure of the pure solvent

This solution that can fulfill Raoult's law is said to be the ideal solution

So the ideal solution occurs if the  attractive  force between the molecules is the same as the attractive  force of each solute and solvent

But not all solutions have ideal properties, so this solution has a deviation or deviation from Raoult's law

There are 2 kinds of deviations from Raoult's Law,

Occurs if the attractive strength between each mixture forming agent is stronger than the  attractive in the mixture

(X-X, Y-Y> X-Y)

This deviation produces a positive enthalpy of solution (ΔH +) which is endothermic so that there is an increase in the volume of the mixture

Occurs if the attractive force in the mixture is stronger than the attractive force of each substance

(X-Y> X-X, Y-Y)

This deviation produces an enthalpy of a negative value solution (ΔH -) which is exothermic so that there is a reduction in the volume of the mixture

So that at a positive deviation, for example, the vapor pressure of the mixed solution will be greater than the initial vapor pressure value

So if

1. X --- X, Y --- Y, and X --- Y are equal

then the value ΔH = 0 and Raoult's Deviation = 0, indicating that the solution is ideal / there is no deviation from Raoult's Law

2. X --- Y is the strongest

then the value ΔH = - and the deviation of Raoult = negative

3. X --- Y is the weakest

then the value ΔH = + and Raoult's Deviation = positive

Raoult's law

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Deviation from Raoult's Law

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The vapor pressure of benzene

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Keywords: Raoult's Law, Deviation, Delta H solution, vapor pressure