Hydrogen hydronium ions

Hydrochloric acid and sulfuric acid are acids because they both taste sour, bum skin, and produce an excess of hydrogen (hydronium) ions in solution. In addition, they turn blue litmus red. 

From this you can see that the cation from the salt comes from the base and the anion comes from the acid. Salts can act as Bronsted-Lowry acids or bases to produce solutions that are acidic or basic. The salts react with water in a reaction known as hydrolysis to yield either a conjugate acid and a hydroxide ion or a conjugate base and a hydrogen (hydronium) ion. If you know the origins of the components of a salt, you can make some predictions about the pH of the solution formed from a hydrolysis of a salt ion. 

When you look at this equilibrium, though, you have to remember that the acid has been spiked with a salt that will increase the concentration of X- to much higher levels than would normally be found (from the dissociation of the acid). That means that the concentration of H+ ions is relatively much smaller than the concentration of XT If an acid is added to the mixture, the equilibrium will be shifted to the left as excess hydrogen (hydronium) ions combine with the conjugate base ... 

The correct answer is (B). From a conceptual perspective, remember that to neutralize an acid you must add enough strong base so that all of the hydrogen (hydronium) ions in the acid combine with the hydroxide ions of the base to form water. Therefore, if you determine the number of moles of hydroxide ions you add to the mixture during the titration, this should equal the number of moles of acid when the solution is neutral. 

Basic solution n. An aqueous solution in, which the concentration of hydroxide ions exceeds that of hydrogen (hydronium) ions. 

Ion product n. (1) The product of the concentrations of hydrogen (hydronium) ions and hydroxide ions in water. (2) The mass-action expression for a solubility equilibrium. 

Acidic Solution n An aqueous solution in which the concentration of hydrogen (hydronium) ions exceeds that of hydroxide ions (Whitten KW, Davis RE, Davis E, Peck LM, Stanley GG (2003) General chemistry. Brookes/Cole, New York). 

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

A Bronsted-Lowry acid is a substance that donates a proton (H+), and a Bronsted-Lowry base is a substance that accepts a proton. (The name proton is often used as a synonym for hydrogen ion, 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, a polar HC1 molecule acts as an acid and donates a proton, while a water molecule acts as a base and accepts the proton, yielding hydronium ion (H30+) and chloride ion (Cl-). 

One could invoke a prior equilibrium between hydrogen peroxide and hydronium ions,... 

First consider acids. When a molecule of an acid dissolves in water, it donates a hydrogen ion, H, to one of the water molecules and forms a hydronium ion, H OT (1). For example, when hydrogen chloride, HC1, dissolves in water, it releases a hydrogen ion to water and the resulting solution consists of hydronium ions and chloride ions ... 

FIGURE 1.2 Acetic acid, like all carboxylic acids, is a weak acid in water. This classification means that most of it remains as acetic acid molecules, CHsCOOH however, a small proportion of these molecules donate a hydrogen ion to a water molecule to form hydronium ions, H.O+, and acetate ions, CH3CO, . 

Once again, we examine acids first. Hydrogen chloride is a strong acid in water. A solution of hydrogen chloride and water, which we call hydrochloric acid, contains hydronium ions, chloride ions, and virtually no HC1 molecules. 

Although hydrogen ions are always attached to water molecules as hydronium ions, H,0, or more complex species, we write them here as H for simplicity. The (aq) should be taken to imply that the hydrogen ion is actually present as the hydronium ion. 

FIGURE 10.1 When an HCl molecule dissolves in water, a hydrogen bond forms between the H atom of HCl (the acid) and the O atom of a neighboring H, 0 molecule (the base). The nucleus of the hydrogen atom is pulled out of the HCl molecule to become part of a hydronium ion. 

Because at equilibrium virtually all the HCl molecules have donated their protons to water, HCl is classified as a strong acid. The proton transfer reaction essentially goes to completion. The H30+ ion is called the hydronium ion. It is strongly hydrated in solution, and there is some evidence that a better representation of the species is H904+ (or even larger clusters of water molecules attached to a proton). A hydrogen ion in water is sometimes represented as H + (aq), but we must remember that H+ does not exist by itself in water and that H CC is a better representation. 

FIGURE 10.15 In a solution of a weak acid, only sonic of the acidic hydrogen atoms are present as hydronium ions (the red sphere), and the solution contains a high proportion of the original acid molecules (HA, gray spheres. The green sphere represents the conjugate base of the acid and the blue spheres are water molecules. The overlay shows only the solute species. 

Sulfides with widely different solubilities and solubility products can be selectively precipitated by adding S2 ions to the solution removed from the chlorides in the first step (see Fig. 11.20). Some metal sulfides (such as CuS, HgS, and Sb2S3) have extremely small solubility products and precipitate if there is the merest trace of S2" ions in the solution. Such a very low concentration of S2 ions is achieved by adding hydrogen sulfide, H2S, to an acidified solution. A higher hydronium ion concentration shifts the equilibrium... 

A possible explanation comes from X-ray analyses of the sulfonic acids [45]. All X-rayed crown ether crystals contained water and the sulfonic acid moiety was dissociated. Therefore in crystals of [45], macrocyclic ben-zenesulfonate anions and hydronium ions (sometimes hydrated) are present. The ions are bound to each other by hydrogen bonds. The size of the included water-hydronium ion cluster (varying by the number of solvating water molecules) depends on the ring size. In the 15-membered ring, HsO" was found, whereas in a 21-membered ring HsO and in the 27-membered ring were present. This means the sulfonic acid functions in [45] are... 

One of the most fundamental chemical reactions is the combination of a hydroxide ion (OH ) and a hydronium ion (H3 0+) to produce two molecules of water OH" (a g) + H3 (a g) 2 H2 O (/) A molecular view of this reaction (Figure 4-7f shows that the hydroxide anion accepts one hydrogen atom from the hydronium cation. Taking account of charges, it is a hydrogen cation (H ) that is transferred. The reaction occurs rapidly when H3 O and OH ions collide. The hydroxide anion accepts a hydrogen cation from the hydronium cation, forming two neutral water molecules. 

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