Concentration: It is the amount of solute present in a given amount of solvent or solution.
Thus, concentration is the ratio of the amount of solute and solvent.
Concentration can be expressed in mass percentage or volume percentage of a solution.
(a) Mass percentage of a solution When the concentration is expressed in mass percentage, it is called concentration by the mass. (b) Volume percentage of a solution When the concentration is expressed in volume percentage, it is called concentration by volume.