Factors affecting solubility


Basically, solubility increases with temperature. It is the case for most of the solvents. The situation is though different for gases. With increase of the temperature they became less soluble in each other and in water, but more soluble in organic solvents.


In most cases solutes dissolve in solvents that have a similar polarity. Chemists use a popular aphorism to describe this feature of solutes and solvents: "Like dissolves like". Nonpolar solutes do not dissolve in polar solvents and the other way roud.


Solid and liquide solutes

For majority of solid and liguide solutes, pressure does not affect solubility.

Gas solutes

As for gasses the Henry's law states that solubility of gas is directly proportional to the pressure of this gas. This is mathematically presented as: p = kc, where k is a tempreture dependent constant for a gas. A good proof of Henry's law can be observed when opening a bottle of carbonated dring. When we decrease the pressure in a bottle, the gas that was dissolved in the drink bubbles out of it.

Molecular size

The larger the molecules of the solute are, the larger is their molecular wieght and their size. It is more difficult it is for solvent molecules to surround bigger molecules. If all of the above mnetioned factors ale excluded, a general rule can be found that larger particles are generaly less soulble. If the pressure, and temperature are the same than out of two solutes of the same polarity, the one with smaller particles is usually more soluble.

Stirring increares the speed of dissolving

Stirring does not have an affect on solubility of a substance, but everyone knows that if he puts sugar in his tea and does not stirr, it will not dissolve. Actually, if we left the tea to stand for a long enough time, the sugar would dissolve. Stirring only increases the speed of the process - it increases move of the solvent what esposes solute to fresh portions of it, thus eabling solubility. As molecules in liquide substances are in costant move, the process would take place anyway, but it would take more time.