reduktionpotentialer

Reduktionpotentialer are a measure of the tendency of a chemical species to gain electrons, i.e., to be reduced, in redox reactions. They are most commonly expressed as standard reduction potentials, E°, relative to the standard hydrogen electrode (SHE) at 25°C in aqueous solution where activities are unity.

Standard reduction potentials are defined for redox couples A^n+/A^(n-1) e− and are determined under standard conditions (1 M, 1 atm, 25°C). The value indicates how readily a species accepts electrons compared with the hydrogen electrode. A positive E° means the couple is a relatively strong oxidizing agent; a negative E° indicates a relatively strong reducing agent. The oxidation potential of the reverse reaction is the opposite sign of the reduction potential (E°ox = -E°red).

The Nernst equation relates E to the actual conditions: E = E° − (RT/nF) ln Q, where Q is the reaction quotient. At 25°C this simplifies to E = E° − (0.05916/n) log10 Q. Consequently, reduction potentials depend on the concentrations, pH (for reactions involving H+), and the solvent.

Common examples at standard conditions include the hydrogen couple (2H+ + 2e− → H2, E° = 0 V), Fe3+/Fe2+ (+0.77 V), Cu2+/Cu (+0.34 V), Zn2+/Zn (−0.76 V), and the oxygen/water couple (+1.23 V in acidic solution). The O2/H2O potential is pH-dependent and shifts with proton concentration.

Applications span electrochemistry, battery design, corrosion science, electrolysis, biosensors, and environmental redox processes. In practice, accurate interpretation requires specifying the solvent, ionic strength, temperature, and pH, as these factors influence measured reduction potentials.