FACTORS THAT AFFECT SOLUBILITY
Molecule Size: Small molecules are often more soluble than larger molecules.
Temperature: When a solid dissolves in a liquid, energy is needed to break the
strong bonds between particles in the solid. At higher temperatures, more energy
is present. Thus, the solubility of most solids increases with temperature.
The interactions between particles in a liquid are not as strong as the
interactions between particles in a solid. No additional energy is needed to dissolve
a liquid in a liquid, thus, the solubility of most liquids is not greatly affected by
temperature.
Gas particles have a great deal of kinetic energy. When a gas dissolves in a
liquid, it loses some energy. At higher temperatures, the dissolved gas gains energy
again, the gas comes out of the solution and is less soluble. Thus, the solubility of
gases decreases with higher temperatures.
The solubility of a solute at any temperature can be determined by using a
solubility curve on a graph of solubility against temperature.
Pressure: Changes in pressure have little effect on solid and liquid solutions. The
solubility of the gas is directly proportional to the pressure of the gas above the
liquid. See Fig. 8.13
SOLUBILITY IN LIQUIDS
An ionic crystal like potassium chloride is extremely polar there is a large
difference in electronegativity – K+ Cl-
A substance such as water is polar but it is not ionic – there is a significant
difference between the electronegativities of oxygen and hydrogen.
A substance such as CCl4 has a small difference in electronegativity (between C
and Cl) but the molecule is non-polar, due to its shape.
A substance such as I2 is non-polar, there is an equal sharing of electrons
Rule of thumb: LIKE DISSOLVES LIKE
Example: KCl will dissolve in H2O but not in CCl4
I2 will dissolve in CCl4 but not in H2O
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