Definition of mass percentage

Mass (or weight) percentage (% w/w) is one of the most often used ways of expressing concentrations. It is defined as

mass percentage definition, eq. 1.11.1

Mass of solution (in case of simple solution containing only one solvent and one solute) is

mass of solution, eq. 1.21.2

so we can formulate the definition in slightly different way:

mass percentage definition 2, eq. 1.31.3

Weight percentage is the only percentage concentration that is always unambiguous. Note that it is expressed in % units (as opposed to % w/v).

Unfortunately bottles labelled % often contain solution of unknown concentration. See what is wrong with percentages for detailed explanation.

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