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Ideal Solution

Ideal solution: Raoult's law holds; ΔH_mix = 0, ΔV_mix = 0
Quick Reference
Formula / NotationIdeal solution: Raoult's law holds; ΔH_mix = 0, ΔV_mix = 0
Also Known AsRaoult's law solution, ideal dilute solution, perfect solution

What is Ideal Solution?

A solution that obeys Raoult's law over all compositions and concentrations. In an ideal solution, solute-solvent interactions are equal to solvent-solvent and solute-solute interactions. Mixing is neither endothermic nor exothermic. Few real solutions are truly ideal.

Formula & Notation

Ideal solution: Raoult's law holds; ΔH_mix = 0, ΔV_mix = 0

Other Names / Synonyms: Raoult's law solution, ideal dilute solution, perfect solution

Properties & Characteristics

An ideal solution is a solution in which the interactions between solute and solvent molecules are the same as those between molecules of the pure components; ΔH_mix = 0 and ΔV_mix = 0. It obeys Raoult's law exactly: P_A = x_A × P°_A over the entire composition range. Real solutions approach ideal behaviour when the components are structurally similar (e.g., benzene-toluene, hexane-heptane). Ideal solutions have positive entropy of mixing: ΔS_mix = −nR Σ x_i ln x_i.

Uses & Applications

The ideal solution model is the reference state for real solutions (activity = concentration for ideal solutions). It simplifies calculations in vapour-liquid equilibrium, osmotic pressure (Van't Hoff equation assumes ideal dilute solution), and phase diagrams. Departures from ideality are quantified by activity coefficients (γ).

Safety Information

No direct safety concern. Real solutions that deviate positively from Raoult's law (azeotropes) may have lower boiling points than expected — relevant for design of distillation operations and prevention of unexpected vapour accumulation in confined spaces.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Ideal Solution
Formula Ideal solution: Raoult's law holds; ΔH_mix = 0, ΔV_mix = 0
Synonyms Raoult's law solution, ideal dilute solution, perfect solution

Frequently Asked Questions

A solution that obeys Raoult's law over all compositions and concentrations. In an ideal solution, solute-solvent interactions are equal to solvent-solvent and solute-solute interactions. Mixing is neither endothermic nor exothermic. Few real solutions are truly ideal.

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