Redokspotensialer

Redokspotensialer, commonly referred to as redox potentials or oxidation–reduction potentials (ORP), describe the tendency of a chemical system to acquire electrons and be reduced. They express the driving force for redox reactions and depend on the relative concentrations of oxidized and reduced species, as well as on pH and temperature.

Potentials are measured with a redox electrode system consisting of a working electrode and a reference electrode (and often a counter electrode). Values are reported relative to a reference, traditionally the standard hydrogen electrode (SHE) for standard redox potentials E°, but in practice many instruments report against Ag/AgCl or other standards. The standard redox potential E° is defined for a specific redox couple under defined conditions, typically 1 M activities and a defined temperature.

The relationship between potential and species concentrations is described by the Nernst equation. At 25°C, for a simple one-electron couple, E ≈ E° − 0.05916/n log([Red]/[Ox]). More generally, E depends on temperature and on the number of electrons transferred, as well as the activities of the involved species.

Applications of redokspotensialer span multiple fields. In environmental science, they indicate oxidation states and mobility of elements in soils and waters. In biology, they relate to cellular respiration and electron transport processes. In industry and water treatment, they help monitor corrosion, process control, and food preservation. Interpreting ORP requires caution: it represents an overall signal from multiple redox couples and can be influenced by pH, complexation, and sensor calibration.