KonzentrationsWirkungsBeziehungen

Konzentrationen (German for concentrations) denote the amount of a substance within a defined space or system. In science, it commonly refers to how much solute is present in a given amount of solvent or solution, and it is a central concept in chemistry, physics, biology, and environmental science.

In chemistry, concentration is commonly expressed in several units: molarity (moles of solute per liter of solution, M), molality (moles per kilogram of solvent, m), mass concentration (grams per liter, g/L), and less commonly, volume fraction and mole fraction. Normality is an older convention that relates to equivalent concepts depending on the reaction.

Concentration is determined by various methods and instruments: gravimetric methods, acid-base titration, UV–visible or infrared spectroscopy, chromatography, and sensor-based techniques. Accurate concentration measurements require calibration with standard solutions and careful consideration of temperature and pressure when applicable.

Applications span many fields. In chemistry, concentrations influence reaction rates, equilibria, and phase behavior. In biology and medicine, the concentrations of ions, metabolites, and drugs govern physiology and treatment. In environmental science, monitoring contaminant concentrations in air, water, and soil is routine for risk assessment and regulation.

Evolution of the concept and notation has been influenced by the development of the SI system, with mol per liter serving as the standard unit for solution concentration, while dimensionless mole fractions are commonly used for gas mixtures and mixtures in thermodynamics.