A system, usually a solution, in which electrochemical reactions occur. It must be sufficiently conducting to allow current to pass - an effect which is often achieved by using a high concentration of electrochemically inert ions.
An electrolyte is a substance containing free ions which behaves as an electrically conductive medium. Because they generally consist of ions in solution, electrolytes are also known as ionic solutions, but molten electrolytes and solid electrolytes are also possible.
Explanation
Electrolytes commonly exist as solutions of acids, bases or salts. Furthermore, some gases may act as electrolytes under conditions of high temperature or low pressure.
Electrolytes are normally formed when a salt is placed into a solvent such as water and the individual atomic components are separated by the force applied upon the solute molecule, in a process called chemical dissociation in which the solution applies force to hold the ions apart.
An electrolyte may be described as concentrated if it has a high concentration of ions, or dilute if it has a low concentration. The properties of electrolytes may be exploited using electrolysis to extract constituent elements and compounds contained within the solution.
Physiological importance
In physiology, the primary ions of electrolytes are sodium(Na+), potassium (K+), calcium (Ca++), magnesium (Mg++), chloride (Cl-), phosphate (PO4---), and bicarbonate (HCO3-).
All higher lifeforms require a subtle and complex electrolyte balance between the intracellular and extracellular milieu. Muscles and neurons are activated by electrolyte activity between the extracellular fluid or interstitial fluid, and intracellular fluid. Electrolytes may enter or leave the cell membrane through specialized protein structures embedded in the plasma membrane called ion channels. (See muscle contraction) Without sufficient levels of these key electrolytes, muscle weakness or severe muscle contractions may occur.
Electrolyte balance is maintained by oral, or in emergencies, intervenous (IV) intake of electrolyte-containing substances, and is regulated by hormones, generally with the kidneys flushing out excess levels. In humans, electrolyte homeostasis is regulated by hormones such as antidiuretic hormone, aldosterone and parathyroid hormone.
Measurement
Measurement of electrolytes is a commonly performed diagnostic procedure, performed via blood testing or urinalysis. Electrolytes measured most often are sodium and potassium. One important test conducted on urine is the specific gravity test to determine the occurrence of electrolyte imbalance.
Nutritional significance
In oral rehydration therapy, electrolyte drinks containing sodium and potassium salts are used to replenish the body's water and electrolyte levels after dehydration caused by exercise, diaphoresis, diarrhea, vomiting or starvation.
Sports drinks such as Gatorade or Lucozade are electrolyte drinks with large amounts of added carbohydrates, such as glucose, to provide energy.
It's really not necessary to replace losses of sodium, potassium and other electrolytes during exercise since you're unlikely to deplete your body's stores of these minerals during normal training. If, however, you find yourself exercising in extreme conditions over 5 or 6 hours (an Ironman or ultramarathon, for example) you will need to add a complex sports drink with electrolytes. The role of sports drinks are to inhibit electrolyte loss, but are insufficient to restore imbalance once it occurs. Medicinal rehydration sachets and drinks are available to replace the key electrolyte ions lost.
Electrolyte and sports drinks can be home-made by using the correct proportions of sugar, salt and water.
Electrolytes in electrochemistry
When two electrodes are placed in an electrolyte and a voltage is applied, the electrolyte will conduct electricity. Lone electrons normally cannot pass through the electrolyte; As a result, a negative charge cloud develops in the electrolyte around the cathode, and a positive charge develops around the anode. The ions in the electrolyte move to neutralize these charges so that the reactions can continue and the electrons can keep flowing.
For example, in a dilute solution of ordinary salt (sodium chloride, NaCl) in water, the cathode reaction will be
2H2O + 2e + H2and hydrogen gas will bubble up; Without the ions from the electrolyte, the charges around the electrode would slow down continued electron flow;
In other systems, the electrode reactions can involve the metals of the electrodes as well as the ions of the electrolyte. electrons flow from one electrode to the other outside of the battery, while inside the battery the circuit is closed by the electrolyte's ions. Here the electrode reactions slowly use up the chemical energy stored in the electrolyte. In some fuel cells, a solid electrolyte or proton conductor connects the plates electrically while keeping the hydrogen and oxygen fuel gases separated. In electroplating tanks, the electrolyte simultaneously deposits metal onto the object to be plated, and electrically connects that object in the circuit. In electrolytic capacitors the chemical effect is used to produce an extremely thin 'dielectric' or insulating coating, while the electrolyte layer behaves as one capacitor plate.
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