Hydronium


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Hydronium

 

a hydrated hydrogen ion in aqueous solution, H3O+. In solution the free hydrogen ion (that is, the nucleus of the hydrogen atom—the proton) is bound to the water molecules in the solution, forming mainly the hydronium ion: H+ + H2O = H3O+. Because of the small size of the proton (10−13 cm; other atoms have radii on the order of 10−8 cm) a strong electrical field is created, and there is covalent bonding between the proton and the unshared pair of electrons of the oxygen atom in water. The formation of the hydronium ion is analogous to the formation of the ammonium ion, NH4+; it has been established that the crystal hydrate of perchloric acid, HClO4H2O, has an ionic crystal lattice that is isomorphic with ammonium perchlorate, NH4+C104. In crystals the H3O+ ion is called oxonium (as distinct from the hydronium ion, H3O+, which is in solution). Because of the association of water molecules, the hydronium ion binds a larger amount of water. The resultant hydrated hydronium ions have the formulas H5O2+, H7O3+, and H9O4+.

REFERENCES

Samoilov, O. Ia. Struktura vodnykh rastvorov elektrolitov i gidratat-siia ionov. Moscow, 1957.
Neniţescu, C. Obshchaia khimiia. Moscow, 1968. (Translated from Rumanian.)
References in periodicals archive ?
The hydroxide ion also forms more-complicated intermediate structures in water than the hydronium ion does.
Acid--(1) A substance containing hydrogen that dissociates to form hydrogen ions when dissolved in water (or which reacts with water to form hydronium ions).
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The pH determination tells the presence of the dissociated hydronium ion.
20] J, is within the range of the energy associated with the second shell of hydrogen that is directly involved with the mobility of protons within the hydronium ion [17].
The low Cd biosorption at pH less than 4 has been suggested to the competition among metal ions from hydronium ions for the available biosorption sites.
Metal sorption starts when the pH rises to the range where most acidic ion exchange sites start to exchange hydronium ion for metal and the capacity reaches the maximum value in the pH range where all the ion exchange sites take part in the reaction and the functional group is able to form complex with the metal cations (37).
The pH of solution is one of the most important factors controlling the adsorption of solid-liquid interface, because both adsorbed molecules and adsorbent particles may have functional groups which are affected by the concentration of hydronium ions ([H.
In the hydrated phase, water moieties bridge the HPA molecules by forming hydronium ions such as [H.
It exchanges [is greater than] 99% of eluent sodium ions for hydronium ions, generating dilute acetic acid that can then be quantitatively removed by vacuum evaporation.
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The interference filter singles out one of water's molecular-vibration spectral bands that is sufficiently far from spectral signatures of other compounds, such as hydronium (OH) radicals, so that the absorption clearly signals the presence of water.