Hydronium ion HjO

Two ions are thus formed protons or hydrogen ions, H, and hydroxyl ions, OH. Free protons are immediately hydrated to form hydronium ions, HjO ... 

In view of the importance of the hydronium ion, HjO, and dissolved oxygen as electron acceptors in corrosion reactions, some values of the redox potentials E and chemical potentials n for the equilibria... 

Hydronium ion, HjO+, is a structural unit in solid perchloric acid hydrate, HCKVHjO, as shown by nuclear magnetic resonance studies. 

The ability of water to ionize, while shght, is of central importance for life. Since water can act both as an acid and as a base, its ionization may be represented as an intermolecular proton transfer that forms a hydronium ion (HjO ) and a hydroxide ion (OH ) ... 

When water undergoes self-ionization, a range of cationic species are formed, the simplest of which is the hydronium ion, HjO (Clever, 1963). This ion has been detected experimentally by a range of techniques including mass spectrometry (Cunningham, Payzant Kebarle, 1972), as have ions of the type H+ (HaO) with values of n up to 8. Monte-Carlo calculations show that HjO ions exist in hydrated clusters surrounded by three or four water molecules in the hydration shell (Kochanski, 1985). These ions have only a short lifetime, since the proton is highly mobile and may be readily transferred from one water molecule to another. The time taken for such a transfer is typically of the order of 10 s provided that the receiving molecule of water is correctly oriented. 

An interesting hydrate is that of the hydronium ion in the gas phase. It consists of a dodecahedral cage of water molecules enclosing the hydronium ion HjO+(H20)20. Each water molecule is bonded to three others in the dodecahedron (Fig. 8.8a). Of the various possible hydrates of H30+ in the gas phase, H3O+(H2O)20 is by far the most slable.21... 

The anion 7-38, which is formed by removal of a proton from one of the amino groups, would not function as a base in this reaction because the equilibrium to form 7-38 is completely on the side of starting material. This can be calculated from values given in Appendix C. The hydronium ion, HjO", (p a = -1.7) is at least 10 times more acidic than the substituted aniline (p a of m-chloroaniline is 26.7). 

The proton released from HA is accepted by water to form the hydronium ion HjO. The reversible ionization reaction can be described by an equilib-... 

A Brensted-Lowry acid is a substance that donates a hydrogen ion (H ), and a Brensted-Lowry base is a substance that accepts H. (The name proton is often used as a synonym for H because loss of the valence electron from a neutral hydrogen atom leaves only the hydrogen nucleus— a proton.) When gaseous hydrogen chloride dissolves in water, for example, an acid-base reaction occurs. A polar HCl molecule donates a proton, and a water molecule accepts the proton, )rielding hydronium ion (HjO ) and chloride ion (Cl ). 

In pure water, small but equal numbers of hydronium ions (HjO" ) and hydroxide ions (OH ) are present. These arise from the partial ionization of water ... 

As discussed in Chapter 15, a hydrogen ion in aqueous solution is closely held hy a water molecule and is better represented as a hydronium ion, HjO (aq). 

Similar errors are also seen with the even more acidic hydronium ion, HjO, where again oxygen cannot exceed its octet and is much more electronegative than hydrogen. 

In acid and base reactions, hydrogen ions are added to molecules or removed from them. A hydrogen ion, often written as H, corresponds to a bare proton. In fact, hydrogen ions exist in solution bound to water molecules, thus forming what are known as hydronium ions, HjO. For simplicity, we will continue to write but we should keep in mind that is shorthand for the actual species present. 

The radiolysis of water produces hydrated electrons (e, ", G = 2.9), hydrogen atoms (G = 0.55) and hydroxyl radicals (G = 2.8) which react with the solute molecules. In addition, the radiolysis of aqueous solutions leads to formation of molecular products H2O2 (G = 0.75) and gaseous hydrogen (G = 0.45). Also produced are hydronium ions (HjO, G = 2.9). In most cases the molecular products do not interfere with the reactions of the radicals. To study the reaction of one radical with the solute without interference from other radicals, scavengers for the other radicals should be added. ... 

Figure 14.8 Proton transfer mechanism ofthe loose complexes R0H---(H20) ---B with a sequential, von Grotthuss-type, hopping of protons through water bridges. For H PTS and monochloroacetate the first transfer to the water bridge forming the hydronium ion HjO+ is ultrafast, and the second transferto the base is slower. (Adapted from Ref [136].)...

In the reaction, a new acid and a new base are formed, which are called the conjugate acid and conjugate base, respectively. The hydronium ion, HjO , is the conjugate acid of the base, H2O, and the acetate ion, CHjCOO , is... 

In any proton-transfer process, the position of equilibrium favors formation of the weaker acid and the weaker base from the stronger acid and base. Alkyloxonium ions (ROH2 ) have approximately the same acidity as hydronium ion (HjO, = 1.7). Thus hydrogen chloride 7) is the... 

A water molecule is a weak electrolyte that dissociates into a proton (H" ) and a hydroxyl ion (OH ). In this process, the proton binds to an adjacent water molecule to which it is hydrogen bonded to form a hydronium ion (HjO+). This interaction is characterized by an equilibrinm constant that for acetic acid is... 

A neutral oxygen atom has 6 valence electrons therefore, oxygen in this species has a formal charge of +1. The species as a whole has a unit positive charge. It is the hydronium ion, HjO. b) The electron count of carbon is 5 there are 2 electrons in an unshared pair, and 3 electrons are counted as carbon s share of the three covalent bonds to hydrogen. 

Hydrogen ions, because of their small size and resulting concentration of positive charge in a small area, however, do not exist as such in water solution. Instead, they bond to water molecules to give hydronium ions (HjO ). Therefore, it is more nearly correct, and as you will see more useful, to write an equation for the ionization of hydrochloric acid (and other acids) with the hydronium ion as a product. 

Figure 11.7 The extent of ionization of a weak acid such as HF (left) and a strong acid such as HCl (right). Initially, there were six HCl and six HF molecules present The strong acid is assumed to be completely ionized in solution. The proton exists in solution as the hydronium ion (HjO ).

The strongest acid that can exist in aqueous solution is the hydronium ion (HjO ). The for the hydronium ion is the equilibrium constant for the following proton exchange reaction ... 

In aqueous systems, the proton always exists as a hydronium ion, HjO. In the Arrhenius acid-base definition, an acid is an H-containing compound that yields HjO in water, a base is an OH-containing compound that yields OH in water, and an acid-base (neutralization) reaction occurs when HjO and OH" form HjO. (Section 18.1)... 

Water molecules surround the proton to form H-bonded species with the general formula H(H20) +. Because the proton is so small, its charge density is very high, so it attracts water especially strongly. The proton bonds covalently to one of the lone electron pairs of a water molecule s O atom to form a hydronium ion, HjO, which forms H bonds to several other water molecules to give species such as 11703, or H(H20)3+ (Figure 18.1). To emphasize the active role of water and the proton-water interaction, the hydrated proton is usually shown in the text as although,... 

We saw in Chapter 1, especially in Table 1.8, that alcohols resemble water in respect to their Brpnsted acidity (ability to donate a proton/rom oxygen). They also resemble water in their Brpnsted basicity (ability to accept a proton on oxygen). Just as proton transfer to a water molecule gives oxonium ion (hydronium ion, HjO ), proton transfer to an alcohol gives an alkyloxonium ion (ROH2 ). 

The reaction mechanisms of this fuel cell, in acid and alkaline electrolytes, are shown in Table 42.2. The major differences, electrochemically, are that the ionic conductor in the acid electrolyte is the hydrogen ion (or, more correctly, the hydronium ion, HjO ) and the OH or hydroxyl ion in the alkaline electrolyte. The only by-product of a hydrogen/oxygen fuel cell is water in the acid electrolyte water is produced at the cathode and, in the alkaline electrolyte fuel cell, it is produced at the anode. 

Leaching, where the mobile alkali ions such as Na in the glass interstices are gradually leached out and replaced by (or the hydronium ion, HjO ) on a no net transfer of charge basis. The reaction may be represented by... 

Hydronium ions (HjO, H70J HgOJ with [CBnH Xg]-, Reed, 1998),... 

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