Expressing Concentration of Solutions

The composition of a solution is defined in terms of concentration. There are several ways to define the concentration of the solution as follows:

Mass percentage (w/w):

The mass percentage of a component of a solution is defined as:

Volume percentage (v/v):

The volume percentage is defined as:

Mass by volume percentage (w/v):

Another unit which is commonly used in medicine and pharmacy is mass by volume percentage. It is the mass of solute dissolved in 100 mL of the solution.

Part per million (ppm):

When a solute is present in trace quantities, it is convenient to express concentration in parts per million (ppm).

Mole fraction:

A commonly used symbol for mole fraction is x and subscript used on the right-hand side of x denotes the component.

Molarity:

Molarity (M) is defined as a number of moles of solute dissolved in one litre (or one cubic decimeter) of the solution,

Molality:

Molality (m) is defined as the number of moles of the solute per kilogram (kg) of the solvent and is expressed as: