massapercentage

Mass percentage, often called mass/mass percentage or weight percent (w/w %), is a way to express the concentration of a component in a mixture. It represents the mass of the solute per mass of the entire solution, multiplied by 100 to yield a percent.

The standard formula is w% = (m_solute / m_solution) × 100%. Here, m_solution is the total mass of the solution, which equals the sum of the solute mass and the solvent (and any other components). If you know the masses of solute and solution, you can calculate w% directly. For example, if 25 g of solute is added to make a solution that weighs 250 g in total, the mass percentage is (25/250) × 100 = 10%.

Mass percentage is a mass-based concentration measurement and is distinct from mole percent, molarity, and molality. It is related to mass fraction, where the fraction is the ratio m_solute / m_solution (a dimensionless value); multiplying by 100 converts it to a percentage. If you know the molar masses and masses, you can convert between mass percent and other concentration units.

Applications of mass percentage include labeling and quality control in chemistry, pharmaceuticals, food, and cosmetics, where precise mass-based concentrations are important. It is independent of temperature in the sense that mass does not change with temperature, though solution density and volume may vary. Caution is warranted when comparing mass percentages across substances with very different densities or when expressing concentrations in terms of volume instead of mass.