The primary concept of interest in this module is concentration. Concentration is calculated by
where
In this context it is assumed that the solute, once it is introduced into a single chamber of water, will be instantaneously and uniformly distributed throughout the water. We call this instantaneous mixing.
There are many different units which can be used to represent concentration. In this module all units are expressed in milligrams per liter (mg/l). Other applications may use units such as parts per billion (ppb), milligrams per milliliter (mg/ml), grams per cubic centimeter (g/cc) or others.
Sometimes the units for the solute are the same as the units for the solvent. In these cases, the concentration is often represented as a percentage.