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The self-ionization of water (also autoionization of water, autoprotolysis of water, autodissociation of water, or simply dissociation of water) is an ionization reaction in pure water or in an aqueous solution, in which a water molecule, H 2 O, deprotonates (loses the nucleus of one of its hydrogen atoms) to become a hydroxide ion, OH −.
Electrolysis of pure water requires excess energy in the form of overpotential to overcome various activation barriers. Without the excess energy, electrolysis occurs slowly or not at all. This is in part due to the limited self-ionization of water. Pure water has an electrical conductivity about one hundred thousandth that of seawater. [8] [9 ...
In chemistry, molecular autoionization (or self-ionization) is a chemical reaction between molecules of the same substance to produce ions. If a pure liquid partially dissociates into ions, it is said to be self-ionizing. [1]: 163 In most cases the oxidation number on all atoms in such a reaction remains unchanged.
Adiabatic ionization is a form of ionization in which an electron is removed from or added to an atom or molecule in its lowest energy state to form an ion in its lowest energy state. [16] The Townsend discharge is a good example of the creation of positive ions and free electrons due to ion impact.
Simply because a substance does not readily dissolve does not make it a weak electrolyte. Acetic acid (CH 3 COOH) and ammonium (NH + 4) are good examples. Acetic acid is extremely soluble in water, but most of the compound dissolves into molecules, rendering it a weak electrolyte. Weak bases and weak acids are generally weak electrolytes.
For example, water undergoes autoprotolysis in the self-ionization of water reaction. 2 H 2 O ⇌ OH − + H 3 O + For example, ammonia in its purest form may undergo autoprotolysis: 2 NH 3 ⇌ NH − 2 + NH + 4. Another example is acetic acid: 2 CH 3 COOH ⇌ CH 3 COO − + CH 3 COOH + 2
The position of equilibrium varies from base to base when a weak base reacts with water. The further to the left it is, the weaker the base. [5] When there is a hydrogen ion gradient between two sides of the biological membrane, the concentration of some weak bases are focused on only one side of the membrane. [6]
The noble gases do not react with water, but their solubility in water increases when going down the group. Argon atoms in water appear to have a first hydration shell composed of 16±2 water molecules at a distance of 280–540 pm, and a weaker second hydration shell is found out to 800 pm. Similar hydration spheres have been found for krypton ...