Raoult’s Law Frequently Asked Questions

What is Raoult’s Law?

Raoult’s law states that partial pressure of a component in a liquid solution is directly propotional to its mole fraction in the solution.

What is Partial Pressure of a Component?

Partial pressure of a component is the pressure which would be exerted by it if only that component is present in the solution’s volume at same temperature.

Do All Solutions Follow Raoult’s Law?

No, only ideal solutions obey Raoult’s law for which enthalpy change and volume change is zero before and after mixing. The vapour pressure of such solutions can be directly determined by Raoult’s law.

What does a Positive Deviation from Raoult’s Law imply?

A positive deviation from Raoult’s law means that vapour pressure of the solution will be higher than that determined by using Raoult’s law. This is due to intramolecular forces between molecules in solution being weaker than the intermolecular forces of the components.

What does a Negative Deviation from Raoult’s Law Imply?

A negative deviation from Raoult’s law means that vapour pressure of the solution will be lower than that determined by using Raoult’s law. This is due to intramolecular forces between molecules in solution being stronger than the intermolecular forces of the components.

Is Raoult’s Law Applicable to Gaseous Mixtures?

Raoult’s law is applied to determine vapour pressure of liquid solution, it may be used for some gaseous mixtures such as ideal gases.

What is Raoult’s Law and Henry’s Law?

• According to Henry’s Law solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid.

• According to Rault’s Law partial vapor pressure of each component of an ideal mixture of liquids is equal to the vapor pressure of the pure component multiplied by its mole fraction in the mixture.

Raoult’s Law in chemistry relates partial pressures of volatile liquid components to their mole fractions in a liquid solution. It states that the partial pressure of each component in the solution is directly proportional to its mole fraction. Thus, it helps us to calculate the total vapour pressure of the solution. Based on Raoult’s law, liquid solutions are classified as Ideal Solutions and Non-Ideal Solutions.

In this article, we will discuss the definition of Raoult’s law, ideal and non-ideal solutions, Raoult’s law for non-volatile solutes and some solved numerical problems based on Raoult’s law.