Chemistry class 12th Ideal and non ideal solutions

Ideal and Non-Ideal Solutions


1. Ideal Solutions

An ideal solution follows Raoult's Law perfectly at all concentrations and temperatures.


Characteristics of Ideal Solutions:
- Obey Raoult's Law: P_A = P_A^0 X_A, P_B = P_B^0 X_B, P_total = P_A + P_B
- No Change in Enthalpy (Delta H_mix = 0): No heat is absorbed or released.
- No Change in Volume (Delta V_mix = 0): No expansion or contraction.
- Similar Intermolecular Forces: A-A, B-B, and A-B interactions are nearly identical.


Examples:
- Benzene + Toluene
- Ethanol + Methanol
- n-Hexane + n-Heptane


2. Non-Ideal Solutions

Non-ideal solutions deviate from Raoult's Law due to different intermolecular forces.


Types of Non-Ideal Solutions:
a) Positive Deviation from Raoult's Law:
- Higher vapor pressure due to weaker A-B interactions.
- Delta H_mix > 0 (Endothermic), Delta V_mix > 0 (Expansion).
- Example: Ethanol + Acetone, Methanol + Water.


b) Negative Deviation from Raoult's Law:
- Lower vapor pressure due to stronger A-B interactions.
- Delta H_mix < 0 (Exothermic), Delta V_mix < 0 (Contraction).
- Example: Acetic Acid + Chloroform, Water + Sulfuric Acid.


3. Azeotropic Mixtures