Reference electrode

, depending on the other electrode and solution. This creates an ionically conductive path to the working electrode of interest. A reference electrode is an electrode that has a stable and well-known electrode potential. The overall chemical reaction taking place in a cell is made up of two independent half-reactions, which describe chemical changes at the two electrodes. To focus on the reaction at the working electrode, the reference electrode is standardized with constant (buffered or saturated) concentrations of each participant of the redox reaction. There are many ways reference electrodes are used. The simplest is when the reference electrode is used as a half-cell to build an electrochemical cell. This allows the potential of the other half cell to be determined. An accurate and practical method to measure an electrode's potential in isolation (absolute electrode potential) has yet to be developed.

, depending on the other electrode and solution. This creates an ionically conductive path to the working electrode of interest.]] A reference electrode is an electrode that has a stable and well-known electrode potential. The overall chemical reaction taking place in a cell is made up of two independent half-reactions, which describe chemical changes at the two electrodes. To focus on the reaction at the working electrode, the reference electrode is standardized with constant (buffered or saturated) concentrations of each participant of the redox reaction. There are many ways reference electrodes are used. The simplest is when the reference electrode is used as a half-cell to build an electrochemical cell. This allows the potential of the other half cell to be determined. An accurate and practical method to measure an electrode's potential in isolation (absolute electrode potential) has yet to be developed. Standard hydrogen electrode (SHE) (E = 0.000 V) activity of H + = 1 Molar Normal hydrogen electrode (NHE) (E ≈ 0.000 V) concentration H + = 1 Molar Reversible hydrogen electrode (RHE) (E = 0.000 V - 0.0591 × pH) at 25 °C Saturated calomel electrode (SCE) (E = +0.241 V saturated) Copper–copper(II) sulfate electrode (CSE) (E = +0.314 V) Silver chloride electrode (E = +0.197 V in saturated KCl) Silver chloride electrode (E = +0.210 V in 3.0 mol KCl/kg) Silver chloride electrode (E = +0.22249 V in 3.0 mol KCl/L) pH-electrode (in case of pH buffered solutions, see buffer solution) Palladium-hydrogen electrode Dynamic hydrogen electrode (DHE) Mercury-mercurous sulfate electrode (MSE) (E = +0.64 V in sat'd K 2 SO 4 , E = +0.68 V in 0.5 M H 2 SO 4 ) ==Pseudo reference electrodes== A pseudo reference electrode is a term that is not well defined and borders on having multiple meanings since pseudo and quasi are often used interchangeably. They are a class of electrodes named pseudo-reference electrodes because they do not maintain a constant potential but vary predictably with conditions. If the conditions are known, the potential can be calculated and the electrode can be used as a reference. Most electrodes work over a limited range of conditions, such as pH or temperature, outside of this range the electrodes behavior becomes unpredictable. The advantage of a pseudo-reference electrode is that the resulting variation is factored into the system allowing researchers to accurately study systems over a wide range of conditions. Yttria-stabilized zirconia (YSZ) membrane electrodes were developed with a variety of redox couples, e.g., Ni/NiO. Their potential depends on pH. When the pH value is known, these electrodes can be employed as a reference with notable applications at elevated temperatures. ==See also== Auxiliary electrode Cyclic voltammetry Table of standard electrode potentials Working electrode

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