According to Raoult's law, which statement is false?

a. The vapor pressure of a solvent over a solution decreases as its mole fraction increases.
b. The solubility of a gas increases as the temperature decreases.
c. The vapor pressure of a solvent over a solution is less than that of pure solvent.
d. The greater the pressure of a gas over a solution the greater its solubility.
e. Ionic solutes dissociate in solution causing an enhancement of all colligative properties.

To determine which statement is false according to Raoult's law, let's quickly review what Raoult's law states.

Raoult's law is applicable to ideal solutions and describes the relationship between the vapor pressure of a solvent and the mole fraction of the solvent in a solution. It can be stated as follows:

The partial vapor pressure of a solvent over a solution is directly proportional to its mole fraction in the solution.

Now, let's analyze each statement and determine if it agrees with Raoult's law:

a. The vapor pressure of a solvent over a solution decreases as its mole fraction increases.
According to Raoult's law, this statement is true. As the mole fraction of the solvent increases, the partial vapor pressure exerted by the solvent decreases.

b. The solubility of a gas increases as the temperature decreases.
This statement is true, but it is not directly related to Raoult's law. The solubility of gases generally follows Henry's law, which states that the solubility of gases in a liquid is directly proportional to the partial pressure of the gas above the liquid.

c. The vapor pressure of a solvent over a solution is less than that of pure solvent.
According to Raoult's law, this statement is true. The vapor pressure of a solvent over a solution is reduced compared to that of the pure solvent due to the presence of other solute molecules.

d. The greater the pressure of a gas over a solution, the greater its solubility.
This statement is also true, but it is not directly related to Raoult's law. According to Henry's law, the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid.

e. Ionic solutes dissociate in solution causing an enhancement of all colligative properties.
This statement is false. Ionic solutes dissociate into ions in a solution, increasing its colligative properties such as boiling point elevation, freezing point depression, and osmotic pressure. However, it is not related to Raoult's law, which specifically focuses on the vapor pressure of the solvent.

Therefore, the false statement, according to Raoult's law, is:
e. Ionic solutes dissociate in solution causing an enhancement of all colligative properties.

The false statement according to Raoult's law is: c. The vapor pressure of a solvent over a solution is less than that of pure solvent.

Since this is not my area of expertise, I searched Google under the key words "Raoult's law" to get these possible sources:

http://en.wikipedia.org/wiki/Raoult's_law
http://en.wikipedia.org/wiki/Vapor_pressure
http://www.chemguide.co.uk/physical/phaseeqia/raoultnonvol.html
http://www.tannerm.com/raoult.htm

In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search.

I hope this helps. Thanks for asking.