(mass concentration of single component mixtures) is: where is the density of the pure component, the volume of the pure component before mixing. Specific volume (or mass-specific volume) Specific volume is the inverse of mass concentration only in the case of pure substances, for which mass concentration is the same as the density of the pure-substance: Molar concentration The conversion to molar concentration is given by: where is the molar mass of constituent . Mass fraction The conversion to mass fraction is given by: Mole fraction The conversion to mole fraction is given by: where is the average molar mass of the mixture. Molality For binary mixtures, the conversion to molality is given by: Spatial variation and gradient The values of (mass and molar) concentration different in space triggers the phenomenon of diffusion. References Chemical properties Density