Standardkalomelelektroden

The Standard Kalomelelektrode, also known as the Standard Hydrogen Electrode (SHE), is a reference electrode used in electrochemistry to measure the standard electrode potential of other electrodes. It is defined as having a potential of zero volts at standard conditions, which are typically 25 degrees Celsius and a pressure of one atmosphere. The electrode consists of a platinum electrode coated with platinum black, immersed in a solution of 1 molar hydrogen ions (H+) at a pH of zero. The hydrogen ions are maintained at a pressure of one atmosphere, ensuring a constant concentration of hydrogen gas (H2) in equilibrium with the solution.

The SHE is a theoretical construct, as it is not practical to maintain a solution with a pH of zero in real-world conditions. However, it serves as a convenient reference point for comparing the potentials of other electrodes. The potential of an electrode relative to the SHE is known as its standard electrode potential (E°). This value is crucial in understanding the spontaneity of redox reactions and the behavior of electrochemical cells.

Despite its theoretical nature, the SHE is often approximated in practical applications using the Standard Calomel Electrode (SCE). The SCE consists of a mercury pool in contact with a solution of potassium chloride (KCl) and mercurous chloride (Hg2Cl2). The potential of the SCE is approximately +0.241 volts relative to the SHE. While not as precise as the SHE, the SCE is more practical for use in laboratory settings.