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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 −.
A new buffer region begins at about pH 11 (pK w − 3), which is where self-ionization of water becomes important. It is very difficult to measure pH values of less than two in aqueous solution with a glass electrode , because the Nernst equation breaks down at such low pH values.
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
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. Such autoionization can be ...
Water is amphoteric, meaning that it can exhibit properties of an acid or a base, depending on the pH of the solution that it is in; it readily produces both H + and OH − ions. [c] Related to its amphoteric character, it undergoes self-ionization. The product of the activities, or approximately, the concentrations of H + and 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 ...
Democrats are licking their wounds after Vice President Harris’s defeat to President-elect Trump, but already are looking toward who might lead their party in a 2028 presidential contest.
An endothermic process may be a chemical process, such as dissolving ammonium nitrate (NH 4 NO 3) in water (H 2 O), or a physical process, such as the melting of ice cubes. [5] The opposite of an endothermic process is an exothermic process, one that releases or "gives out" energy, usually in the form of heat and sometimes as electrical energy. [1]