Acid aqueous solution weak acids ionize only

A substance that produces H+(aq) ions in aqueous solution. Strong acids ionize completely or almost completely in dilute aqueous solution. Weak acids ionize only slightly. 

Weak acids ionize only slightly (usually less than 5%) in dilute aqueous solution. Some common weak acids are listed in Appendix F. Several of them and their anions are given in Table 4-6. 

Strong acids and bases ionize completely in aqueous solutions. Weak acids and bases ionize only partially in aqueous solutions. An acid-base reaction is shown below. A titration was done by adding a base to a known concentration and fixed volume of an acid. The reaction follows ... 

We categorize acids arxJ bases as being either strong or weak electrolytes. Strong acids and bases are strong electrolytes, ionizing or dissociating completely in aqueous solution. Weak acids and bases are weak electrolytes and ionize only partially. 

In contrast to strong bases, a weak base ionizes only partially in dilute aqueous solution to form the conjugate acid of the base and hydroxide ion. The weak base methylamine (CH3NH2) reacts with water to produce an equilibrium mixture of CH3NH2 molecules, CH3NH3+ ions, and OH ions. 

On the other hand, acetic acid (a weak acid) is only slightly ionized in dilute aqueous solution. Acetate ions have a strong tendency to react with H3O+ to form CH3COOH molecules. Acetic acid ionizes only slightly. 

As you know, acetic acid is a weak acid. In a solution of acetic acid, only a small fraction of the acetic acid molecules ionize. Other than water, the major particle present in an aqueous solution of acetic acid is HC2H3O2. NaOH, as seen before, completely dissociates. The ionic equation shows what is present when the acid and base react. As in the previous cases, the salt is also written as dissociated ions. 

Most acidic substances are weak acids and therefore only partially ionized in aqueous solution ( FIGURE 16.9). We can use the equilibrium constant for the ionization reaction to express the extent to which a weak acid ionizes. If we represent a general weak acid as HA, we can write the equation for its ionization in either of the following ways, depending on whether the hydrated proton is represented as H.30 aq) or H aq) ... 

HF is a weak acid that only partially ionizes in solution. If an aqueous solution that is... 

The ionization is reversible. The anion (acting as a weak base) can recombine with the hydrogen ion to reform neutral HA. Both reactions occur continuously in solution, with the extent of ionization dependent on the strength of the acid. Strong acids, such as HC1, ionize completely in dilute aqueous solution. Thus a 0.01 molar (10-2 molar) solution has a pH of 2. Weak acids, such as acetic and other organic acids, ionize only slightly in solution and form solutions with pH from 4 to 6. 

HCl(aq), a soluble gas, ionizes almost totally into its ions in aqueous solution, whereas glucose, a soluble molecular solid, does not ionize at all. Weak acids, such as HF, are soluble in water but ionize only slightly into ions. 

Dilute aqueous solutions of weak acids, such as HF and HN02, contain relatively few ions because they are weak electrolytes, ionize only slightly into their ions and are therefore, poor conductors of electricity. This can be demonstrated using a conductivity apparatus as shown in Figure 6-1. 

The discussion in the previous sections concerning solvated species indicates that a complete knowledge of the chemical reactions that take place in a system is not necessary in order to apply thermodynamics to that system, provided that the assumptions made are applied consistently. The application of thermodynamics to sulfuric acid in aqueous solution affords another illustration of this fact. We choose the reference state of sulfuric acid to be the infinitely dilute solution. However, because we know that sulfuric acid is dissociated in aqueous solution, we must express the chemical potential in terms of the dissociation products rather than the component (Sect. 8.15). Either we can assume that the only solute species present are hydrogen ion and sulfate ion (we choose to designate the acid species as hydrogen rather than hydronium ion), or we can take into account the weak character of the bisulfate ion and assume that the species are hydrogen ion, bisulfate ion, and sulfate ion. With the first assumption, the effect of the weakness of the bisulfate ion is contained in the mean activity coefficient of the sulfuric acid, whereas with the second assumption, the ionization constant of the bisulfate ion is involved indirectly. 

Partially ionized substances are written in the ionic form only if the extent of ionization is appreciable (about 20 percent or more). Water, which is ionized to the extent of less than one part in a hundred million, is written as H20 (or, if more convenient, HOH). Strong acids, like HC1 and HNO3, may be written in the ionized form, but weak acids, like nitrous, acetic, and sulfurous acids, are written in the molecular form (HNO2, HC2H3O2 and H2SO3). Ammonia, a weak base, is written NH3. Sodium hydroxide, a strong base, is written in the ionized form when in aqueous solution. 

The organic solvent phase containing only weakly acidic and neutral compounds is sequentially back-extracted with an aqueous (pH 10) solution of sodium hydroxide (Figure 2.16, step 4). Neutral compounds remain in the organic solvent phase, while weak organic acids, ionized at this pH, will be extracted into the aqueous phase. 

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