Percentage Purity
The proportion of a sample that consists of the desired compound, expressed as a percentage of the total mass.
Formula / equation
% purity = (mass pure / mass sample) × 100
Unit
Dimensionless
In depth
Impure reagents must be corrected for purity before any stoichiometric calculation, since only the pure fraction reacts. Purity is determined by titration against a primary standard, by chromatographic peak area, or by measuring the mass of a product formed in a reaction of known stoichiometry.
Examples in the real world
A 5.00 g limestone sample yielding 2.10 g of CO₂ works back to 95.5% CaCO₃.