HCl is a powerful electrolyte



A electrolyte (from agr. ηλεκτρόν electron, "Amber" i.ü.S "electric" and agr. Λυτικός lytikós, "Dissolvable") is a substance that conducts the electric current when a voltage is applied under the influence of the resulting electric field (2nd class conductor), whereby its electrical conductivity and the charge transport are brought about by the directional movement of ions. In addition, chemical processes occur on the electrodes. Like ionized gases, electrolytes are ionic conductors. The conductivity of electrolytes is less than is typical for metals; Metals are therefore called 1st class conductors.

Classification

In the broadest sense, electrolytes are substances that are at least partially present as ions. One differentiates

  • strong electrolytesthat are completely split into ions when dissolved, such as table salt.
  • weak electrolytesthat only partially dissociate in solution, such as acetic acid.

For the conductivity of dissolved electrolytes, see electrolytic conductivity.

Examples:
NaCl(s) → Well+(aq) + Cl-(aq)
NaOH(s) → Well+(aq) + OH-(aq)
  • At a potential electrolyte on the other hand, the ions are only created through the reaction with the solvent.
Example:
HCl(G) + H2O → Cl-(aq) + H3O+

The most important electrolytes are therefore either acids, bases or salts.

liquids

Electrolytes in the sense of ion conductors require mobile ions. Therefore, all liquids that contain ions are electrolytes. Liquid electrolytes are molten salts and ionic liquids as well as all liquid solutions of ions. In extreme cases, molten salts and ionic liquids consist only of ions, but they can contain dissolved molecules. In the case of aqueous or organic electrolyte solutions, it is the other way round: Here the solvent consists of molecules and the ions are dissolved in it. The production of an electrolyte solution can consist in the simple dissolution of already existing ions, or in a chemical reaction in which ions are formed, for example an acid-base reaction such as the dissolution of molecules such as hydrogen chloride or ammonia in water.

Solid

Solids can also contain mobile ions. Especially at high temperatures, ions become mobile in solids consisting of ions, for example. But there are also solid electrolytes that can be used at room temperature or at only slightly elevated temperatures. This also includes the polymer electrolyte membranes used in some fuel cells. They consist of a plastic framework that contains ionic side groups. Important ion conductors are z. B. some sodium aluminates. In addition to their use in fuel cells, solid electrolytes are also important in sensors, such as the lambda probe, which contain an electrolyte that conducts oxygen ions (e.g. YSZ, yttria stabilized zirconia, a mixture of zirconium dioxide ZrO2 and yttria Y2O3). The Nernst lamp, commonly used as an incandescent lamp around 1900, also used such solid electrolytes.

Biological electrolytes

The most important ions of biological electrolytes are sodium, potassium, calcium, magnesium, chloride, phosphate and hydrogen carbonate. They are contained in the cytosol and are indispensable for the function of the cells. Other ions are also necessary as trace elements for the cell, but the ions mentioned are particularly important with regard to the electrolyte balance of the cell, since they play an outstanding role in regulating the osmotic pressure.

physiology

All higher forms of life maintain a subtle and complex electrolyte balance between their intracellular (inside their cells) and extracellular (outside or between their cells) environments. In particular, maintaining accurate osmotic gradients is important. These gradients influence and regulate the body's water balance and the pH of the blood. Electrolytes also play a key role in the functioning of nerve or muscle cells. The electrolyte concentration in the cell is regulated with the help of ion channels.

The electrolyte balance is maintained through the oral supply and intestinal absorption of food and substances containing electrolytes and is regulated by hormones. An excess is generally excreted via the kidneys. In humans, the homeostasis (self-regulation) of the salts is controlled by hormones such as antidiuretic hormone (ADH), aldosterone and parathyroid hormone (PTH).

The causes of disturbances in the electrolyte balance can be electrolyte losses (e.g. due to diarrhea, vomiting) or disturbances of the endocrine glands. Serious electrolyte imbalances can lead to cardiac arrhythmias and nerve damage and are mostly medical emergencies.

The electrolytes are measured using blood and urine tests. The interpretation of these values ​​is difficult without considering the anamnesis and often impossible without a simultaneous examination of the kidney function. The most commonly studied electrolytes are sodium and potassium. Chloride levels are rarely measured because it is inherently related to sodium levels.

See also: Tyrode

Electrolyte-containing drinks with sodium and potassium salts are used to replenish electrolytes after dehydration. This loss of fluids and thus electrolytes is caused by profuse sweating (physical work), diarrhea, vomiting, excessive alcohol consumption or malnutrition. Pure distilled water is not helpful as it removes salts from the body's cells and impairs their chemical functions. This can lead to overhydration.

In addition to electrolytes, sports drinks contain large amounts of carbohydrates (e.g. glucose) as a source of energy. Due to the high sugar content, they are not suitable for children in the long term. Prevention of dental caries is also recommended for long-term adult users.

The over-the-counter drinks are usually isotonic, that is, their osmolarity is close to that of blood. Hypotonic (lower osmolarity) and hypertonic (higher osmolarity) drinks are available for competitive athletes, depending on their particular nutritional needs.

You can also make electrolyte and sports drinks yourself with the right proportions of sugar, salt and water.

Electrochemical Applications

An important application of electrolytes is in electrolysis, including electroplating. Electrolytes are also necessary components of batteries, accumulators and electrolytic capacitors. For the origin of the term electrolyte coined by Michael Faraday, see also “Faraday's Laws”, for the meaning of the electrolyte concentration see also Nernst equation.

See also

Electrolyte database Regensburg

Category: Electrochemistry