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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 −.
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.
3.6 Self-ionization. ... Download as PDF; Printable version; ... drought is an extended period of months or years when a region notes a deficiency in its water supply.
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
Notes For a given acid or base in water, pK a + pK b = pK w, the self-ionization constant of water. The association constant for the formation of a supramolecular complex may be denoted as K a; in such cases "a" stands for "association", not "acid".
Because water is the solvent, and has an activity of one, the self-ionization constant of water is defined as K w = [ H + ] [ O H − ] {\displaystyle K_{\mathrm {w} }=\mathrm {[H^{+}][OH^{-}]} } It is perfectly legitimate to write [H + ] for the hydronium ion concentration, since the state of solvation of the proton is constant (in dilute ...
In chemistry, hydronium (hydroxonium in traditional British English) is the cation [H 3 O] +, also written as H 3 O +, the type of oxonium ion produced by protonation of water.It is often viewed as the positive ion present when an Arrhenius acid is dissolved in water, as Arrhenius acid molecules in solution give up a proton (a positive hydrogen ion, H +) to the surrounding water molecules (H 2 O).
K w is the equilibrium constant for self-ionization of water, equal to 1.0 × 10 −14. Note that in solution H + exists as the hydronium ion H 3 O +, and further aquation of the hydronium ion has negligible effect on the dissociation equilibrium, except at very high acid concentration. Figure 2.