The deviation from ideal behavior in this case is called negative deviation. Here's why:
* Ideal solutions: Ideal solutions assume no heat is absorbed or released during mixing (enthalpy of solution is zero). They also assume no volume change upon mixing.
* Negative deviation: When heat is released (exothermic), the intermolecular forces between the solute and solvent molecules are stronger than those between the pure components. This leads to a more ordered state, a decrease in volume, and a negative enthalpy of solution.
Examples of negative deviations:
* Mixing sulfuric acid (H₂SO₄) and water: This generates significant heat, even causing the mixture to boil if not done carefully.
* Mixing ethanol and water: This also releases heat and leads to a decrease in the total volume.
In summary:
* Exothermic solution: Heat is released.
* Negative deviation: Stronger interactions between solute and solvent molecules compared to the pure components. This leads to a more ordered state, a decrease in volume, and a negative enthalpy of solution.
