Raoult’s Law and Deviations

Binary Liquid Solutions

• In a binary liquid solution where both components are volatile, the total pressure is calculated using Raoult's law.

Deviations from Raoult's Law

• Positive deviations from Raoult's law are observed in solutions where the intermolecular forces between the components are weaker than the forces between the same molecules.
• Negative deviations from Raoult's law are observed in solutions where the intermolecular forces between the components are stronger than the forces between the same molecules.

Properties of Solutions

• The properties of solutions that depend on the number of solute particles regardless of their chemical identity are colligative properties.

Osmotic Pressure

• Applying a pressure higher than the osmotic pressure to a solution can reverse the process of osmosis.

Henry'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.

Vapor Pressure of a Solvent

• The vapor pressure of a solvent is lowered by a non-volatile solute according to Raoult's law.

Negative Deviations from Raoult's Law

• Mixtures like phenol and aniline show negative deviations from Raoult's law because of the formation of hydrogen bonds between the components.
• The characteristic of a mixture that leads to negative deviations from Raoult's law is the formation of strong intermolecular forces between the components.

Azeotrope Formation

• Solutions showing large positive deviations from Raoult's law form a minimum boiling azeotrope.

Hydrogen Bonds and Vapor Pressure

• The formation of hydrogen bonds between chloroform and acetone reduces their vapor pressures.
• The main reason behind the negative deviations from Raoult's law in mixtures like chloroform and acetone is the formation of hydrogen bonds between the components.

Binary Mixtures

• A binary mixture with the same composition in both liquid and vapor phases is called a zeotrope.

Positive Deviations from Raoult's Law

• A solution shows positive deviation from Raoult's law when the intermolecular forces between the components are weaker than the forces between the same molecules.
• Adding acetone to pure ethanol disrupts the hydrogen bonds between the ethanol molecules, increasing the vapor pressure.
• In a solution showing positive deviation, the vapor pressure is higher than that of the pure solvent.
• The interaction that is weaker in a solution showing positive deviation from Raoult's law is the intermolecular force between the components.

Dipolar Interactions

• Adding carbon disulphide to acetone disrupts the dipolar interactions between the acetone molecules, increasing the vapor pressure.

Laws Associated with Deviations

• Raoult's law is associated with deviations such as positive and negative deviation from ideal behavior in solutions.