Aqueous Solutions

An aqueous solution is a solution in which the solvent (a solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gas) is water. The word aqueous means pertaining to, related to, similar to, or dissolved in water. As water is an excellent solvent as well as naturally abundant, it is a ubiquitous solvent in chemistry.

Substances that do not dissolve well in water are called hydrophobic ('water fearing') whereas those that do are known as hydrophilic ('water-loving'). An example of a hydrophilic substance would be sodium chloride (ordinary table salt). Acids and bases are aqueous solutions.

The ability of a substance to dissolve in water is determined by whether the substance can match or exceed the strong attractive forces that water molecules generate between themselves. If the substance lacks the ability to dissolve in water the molecules form a precipitate.

Aqueous solutions that conduct electric current efficiently contain strong electrolytes, while ones that conduct poorly are considered to have weak electrolytes. Those strong electrolytes are substances that are completely ionised in water, whereas the weak electrolytes exhibit only a small degree of ionisation in water.

Nonelectrolytes are substances that dissolve in water, but which maintain their molecular integrity (do not dissociate into ions). Sugar is a good example of a nonelectrolyte.

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