Solutions Intermolecular Forces Compounds  Elmhurst College
Review of Solutions: Solubility of Polar Solutes Temperature & Pressure  Chemistry Department
Solubility of Salts Non-polar Solutes    Virtual ChemBook

SOLUTION INTERMOLECULAR FORCES

Review of Solutions:

A solution is a mixture of two or more substances in a single phase. At least two substances must be mixed in order to have a solution. The substance in the smallest amount and the one that dissolves or disperses is called the SOLUTE. The substance in the larger amount is called the SOLVENT. In most common instances water is the solvent. The gases, liquids, or solids dissolved in water are the solutes.

Introduction:

The dissolving process involves a consideration of the relative strength of three intermolecular attractive forces. The type of forces between solute-solute molecules and solvent-solvent molecules must be considered. These intermolecular attractions must be broken before new solute-solvent attractive forces can become effective. Perhaps the bond breaking and bond forming processes take place simultaneously.

A solute will dissolve in a solvent if the solute-solvent forces of attraction are great enough to overcome the solute-solute and solvent-solvent forces of attraction. A solute will not dissolve if the solute-solvent forces of attraction are weaker than individual solute and solvent intermolecular attractions. Generally, if all three of the intermolecular forces of attraction are roughly equal, the substances will be soluble in each other.

Solubility Rule and Summary

LIKES DISSOLVE LIKES.

This means that ionic or polar solutes dissolve in polar solvents.
Non-polar solutes dissolve in non-polar solvents.

Polar and ionic solutes DO NOT dissolve in non-polar solvents and vice versa.

Remember that when applying the solubility rule: "Likes Dissolve Likes", that there are no absolutes and there are exceptions with a small amount of solubility possible. The rule is most useful when making comparisons between a series of compounds.