Bases ionization in water

We say that strong acids, weak acids, and weak bases ionize in water, but strong bases dissociate in water. What is the difference between ionization and dissociation ... 

Arrhenius acids ionize in water to give H" ions, and Arrhenius bases ionize in water to give OH ions. Brpnsted acids donate protons, and Brpnsted bases accept protons. 

A base ionizes in water to give hydroxyl ions. Weak (partially ionized) bases generally ionize as follows ... 

The extent to which acids or bases ionize in water is described in terms of either the degree of ionization (a) or the percent ionization. For the ionization of an acid, HA, we define the degree of ionization as follows. 

The equilibrium constant for the reaction of an acid with water is called the acid ionization constant (K ), equation (16.10), and that for the reaction of a base with water is called the base ionization constant (K, ), equation (16.13). Strong acids and strong bases have large ionization constants (Xa or Kb >i> 1) and are essentially completely ionized in water. Weak acids and weak bases have small ionization constants K or Xt, 1) and ionize to a limited extent in water. The extent to which acids or bases ionize in water is described in terms of either the degree of ionization (a) (equation 16.15) or the percent ionization (equation 16.16). For a weak acid or weak base, the degree of ionization increases with increasing dilution. 

Base According to the Arrhenius definition (Section 1 12) a substance that ionizes in water to produce hydroxide ions According to the Brpnsted-Lowry definition (Section 1 13) a substance that accepts a proton from some suitable donor According to the Lewis definition (Section 1 17) an electron pair donor... 

Electron Delocalization in the Conjugate Base. With a pK of —1.4, nitric acid is almost completely ionized in water. If we look at the Lewis structure of nitric acid in light of what we have said about inductive effects, we can see why. The N atom in nitric acid is not only electronegative in its own right, but bears a formal charge of +1, which enhances its ability to attract electrons away from the —OH group. 

According to the Arrhenius definitions, an acid ionizes in water to produce protons (H" ) and a base produces hydroxide ions (HO ). The strength of an acid is given by its equilibrium constant for ionization in aqueous solution ... 

As we have pointed out, strong acids and bases are completely ionized in water. As a result, compounds such as HC1 and NaOH are strong electrolytes like NaCl. In contrast, molecular weak acids and weak bases are poor conductors because their water solutions contain relatively few ions. Hydrofluoric acid and ammonia are commonly described as weak electrolytes. 

The fact that strong acids and bases are completely ionized in water makes it relatively easy to calculate the pH and pOH of their solutions (Example 13.3). 

As pointed out in Chapter 13, strong acids ionize completely in water to form H30+ ions strong bases dissolve in water to form OH- ions. The neutralization reaction that takes place when any strong acid reacts with any strong base can be represented by a net ionic equation of the Bronsted- Lowry type ... 

Strong base A base that completely ionizes in water. 

Weak base A base that does not completely ionize in water. 

Ans. Strength refers to the extent the acid or base will ionize in water. Concentration is a measure of the quantity of the acid or base in a certain volume of solution. 

Strong acids completely dissociate (ionize) in water. Weak acids partially dissociate and establish an equilibrium system. There is a large range of weak acids based upon their ability to donate protons. Consider the general weak acid HA and its reaction when placed in water ... 

The strength of an acid or base can be determined by considering the extent to which it ionizes in water. 

The crosslinking of the ionic copolymer is carried out by the addition of a metal compound to the base copolymer. The metal compound, which is employed must have at least one of its valences satisfied by a group which is substantially ionized in water. The necessary ionization is determined by the water solubility of the metal when bonded solely to the ionizable salt group (6). 

Bases are those substances that ionize in water to release OH- ions. NaOH is a strong base, ionizing completely in water to yield Na+ and OH- ions. However, even those hydroxide bases that do not dissolve... 

Weak bases are able to accept hydrogen ions from acids, but they are less determined to do so than strong bases. Weak bases do not completely ionize in water... 

Strong bases completely ionize in water. This means every mole of strong base falls apart into an equal number of moles of hydroxide ions, except for Ba(OH)2 which gives two moles of hydroxide ions per mole. Therefore, [OH-] is equal to the formal concentration of the base. 

NaCI is present in solution as ions. Compounds that are completely ionized in water are called strong electrolytes because these solutions easily conduct electricity. Most salts are strong electrolytes. Other compounds (including many acids and bases) may dissolve in water without completely ionizing. These are referred to as weak electrolytes and their state of ionization is at equilibrium with the larger molecule. Those compounds that dissolve with no ionization (e.g., glucose, C6H12O6) are called nonelectrolytes. 

The acidity constant is a measure of the strength of an acid. If the acidity constant for a particular acid is near 1, about equal amounts of the acid and its conjugate base are present at equilibrium. A strong acid, which dissociates nearly completely in water, has an acidity constant significantly greater than 1. A weak acid, which is only slightly dissociated in water, has an equilibrium constant significantly less than 1. The acidity constant for acetic acid is 1.8 X 10-5—only a small amount of acetic acid actually ionizes in water. It is a weak acid. 

Ammonia is a weak base, having Kb = 1.8 x 10 5, and it ionizes in water according to the following equation ... 

Strong acids and bases react violently and produce heat and, hence, are not very useful in forming CBCs. Therefore, in the entire study of CBPCs, we will be dealing with phosphoric acid, which is a weak acid in that it dissolves in water slowly compared with strong acids such as hydrochloric acid. Acid phosphates such as KH2PO4 and A1(H2P04)3 and weak bases such as oxides of Mg and A1 dissolve slowly in water. To represent how slowly the weak acids or bases dissolve in water and to what extent, the term dissociation (ionization) constant is used. 

Surfactants are divided into three main groups, based on their ionization in water these are anionic surfactants, cationic surfactants, and nonionic surfactants. If on ionization, one end of the molecule becomes a negative ion, the surfactant is known as an anionic surfactant as shown in Figure 2.3. 

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