Types of Solutions

A solution is a homogeneous mixture of two or more substances, made up of atoms, ions or molecules distributed uniformly throughout. Whichever component is present in the largest amount is called the solvent; every other component is a solute.

Worked illustration. When a small amount of NaCl is dissolved in water, the resulting solution is homogeneous: Na$^+$ and Cl$^-$ ions are spread uniformly through the water. Since the amount of water present is far larger than the amount of NaCl, water is the solvent and NaCl is the solute.

Aqueous vs non-aqueous. If water is the solvent, the solution is called an aqueous solution. If some other solvent is used instead -- benzene, carbon tetrachloride, ether, and so on -- the solution is called a non-aqueous solution.

Nine possible types of solution. The most familiar solutions dissolve a solid solute in a liquid solvent, but in principle solute and solvent can each independently be a solid, a liquid or a gas, giving nine combinations in total (Table 9.1):