Mechanisms of Solute-Solvent Interactions

Solute-Solvent Interactions & Solubility is largely determined by the interactions between solute and solvent molecules.

Steps Involved in the Dissolution of a Solute

1. Detachment of Solute Particles:

   • Solute particles separate from the bulk solute.
   • Requires energy to overcome intermolecular forces.

2. Formation of Vacant Sites in Solvent:

   • Solvent molecules rearrange to create vacant sites.
   • These sites will accommodate solute particles.

3. Insertion of Solute Particles into Solvent:

   • Detached solute particles fit into the vacant sites in the solvent.
   • Results in the formation of a homogeneous solution.

Types of Solute-Solvent Interactions

1. Ionic Interactions:

   1. Ion-Dipole Interactions: Ionic solutes (e.g., salts) dissolve in polar solvents (e.g., water) by interacting with solvent dipoles.
   2. Ion Pairing: High solute concentrations may form ion pairs, affecting solubility.

2. Polar Interactions:

   1. Hydrogen Bonding: Hydrogen bonds form between solute and solvent molecules, enhancing solubility for substances like alcohols and carboxylic acids.
   2. Dipole-Dipole Interactions: Weaker than hydrogen bonds but contribute to solubility in polar molecules.

3. Non-Polar Interactions:

   1. Van der Waals Forces: Weak forces in non-polar solvents (e.g., hexane) due to temporary dipoles.
   2. Hydrophobic Interactions: Non-polar solutes aggregate in water, resulting in low solubility.

4. Amphiphilic Interactions:

   1. Micelle Formation: Amphiphilic molecules (e.g., surfactants) form micelles in water, trapping hydrophobic solutes and increasing apparent solubility.

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