What solutes can water dissolve and why

The major factor that determines whether solutes dissolve in solvents is entropy.

To form a solution we must:
1. Separate the particles of the solvent.
2. Separate the particles of the solute.
3. Mix the particles of solvent and solute.

and are both positive because it requires energy to pull molecules away from each other. is negative because intermolecular attractions are forming.

For the solution process to be favourable, should at least equal .

Nonpolar Solvent – Nonpolar solute

If both solvent and solute are nonpolar, all the values are small. The major factor then is the increase in entropy (disorder) that occurs when a solution forms. This is a favourable process.

Polar Solvent – Polar Solute

If both solvent and solute are polar, all the values are large but similar in size. The major factor again is the increase in entropy.


Polar Solvent – Nonpolar Solute
If a nonpolar solute such as oil mixes with a polar solvent like water, is large and positive. This outweighs . A solution does not form.