Acid-Base Reactions in Aqueous Solutions

CHAPTER 10 REACTIONS IN AQUEOUS SOLUTIONS I ACIDS, BASES, AND SALTS 

Similarly, comparison of the acid strengths of nitric acid, HNO3, and nitrous acid, HNO2, shows that HNO3 is a much stronger acid than HNO2. 

Acid strengths of most ternary acids containing the same central element increase with 

The following orders of increasing acid strength are typical. 

In mosf ternary Inorganic acids, the H atoms are bonded to the 0 atoms. But It Is very Important to be sure of their structures before comparing them. The phosphorus-containing ternary acids are more complicated and can have both P — H and 0 — H bonding. 

---

In this chapter, we will focus on acid-base reactions in aqueous solutions. Such solutions play important roles in our daily lives. Vinegar, oranges, apples, grapes, and lemons are some familiar acid-containing substances, and most household cleaning products are base-containing substances. 

Note that A is called the conjugate base of HA and BH+ the conjugate acid of B. Proton transfer reactions as described by Eq. 8-1 are usually very fast and reversible. It makes sense then that we treat such reactions as equilibrium processes, and that we are interested in the equilibrium distribution of the species involved in the reaction. In this chapter we confine our discussion to proton transfer reactions in aqueous solution, although in some cases, such reactions may also be important in nonaqueous media. Our major concern will be the speciation of an organic acid or base (neutral versus ionic species) in water under given conditions. Before we get to that, however, we have to recall some basic thermodynamic aspects that we need to describe acid-base reactions in aqueous solution. 

So far, we have used the pure liquid compound as reference state for describing the thermodynamics of transfer processes between different media (Chapter 3). When treating reactions of several different chemical species in one medium (e.g., water) it is, however, much more convenient to use the infinite dilution state in that medium as the reference state for the solutes. Hence, for acid-base reactions in aqueous solutions, in analogy to Eq. 3-34, we may express the chemical potential of the solute i as ... 

We will now deal with the stoichiometry of acid-base reactions in aqueous solutions. The procedure is fundamentally the same as that used previously. 

Acid-base reactions in aqueous solutions are of central importance in a wide variety of systems that include industrial manufacturing processes, ordinary household substances, and the life-sustaining reactions in living systems. The common feature shared by all acids and bases is that they modify the properties of the water in which they are dissolved. An acid increases the concentration of the hydronium ion above its value in pure water, which is controlled by the ion product... 

From the definitions of an acid, it must be clear that, if there is an acid in a reaction, there must also be a base you can t have a proton donated without something to accept it. We can write a hypothetical acid-base reaction in aqueous solution as follows ... 

U22J ACID-BASE REACTIONS IN AQUEOUS SOLUTIONS... 

Some of the most important processes in chemical and biological SYSTEMS ARE ACID-BASE REACTIONS IN AQUEOUS SOLUTIONS. In THIS FIRST OF TWO CHAPTERS ON THE PROPERTIES OF ACIDS AND BASES, WE WILL STUDY THE DEFINITIONS OF ACIDS AND BASES, THE pH SCALE, THE IONIZATION OF WEAK ACIDS AND WEAK BASES, AND THE RELATIONSHIP BETWEEN ACID STRENGTH AND MOLECULAR STRUCTURE. WE WILL ALSO LOOK AT OXIDES THAT CAN ACT AS ACIDS OR BASES. 

In the study of acid-base reactions in aqueous solutions, the hydrogen ion concentration is key, because it indicates the acidity or basicity of the solution. Expressing the proton as rather than H30, we can write the equilibrium constant for the autoionization of water, Equation (15.1), as... 

The change in pH obtained by laser excitation was monitored directly by exciting 2-naphthol 6-sulfonate or 2-naphthol-3,6-disulfonate in the presence of pH indicator dyes. The appartus used in this study is shown in Fig. 16. The acid-base reactions in aqueous solution of 2-naphthol-3,6-disulfonate following a laser pulse at 347.2 nm are given in Scheme V, where In is a pH indicator. 

Acid-base reactions in aqueous solutions generally proceed extremely rapidly. The reaction. 

Some of the most important processes in chemical and biological systems are acid-base reactions in aqueous solutions. In this first of two chapters on the properties of acids and bases, we will study the definitions of acids and bases, the pH scale, the ionization of weak acids and weak bases, and the relationship between acid strength and molecular structure. We will also look at oxides that can act as acids and bases. 

The ability of water molecules to accept and donate protons is the basis of acid-base reactions in aqueous solution. The electrostatic potential map shows the transfer of a proton between two water molecules to form a hydronium ion and a hydroxide ion. 

The Bronsted-Lowry Theory 10-5 The Autoionization of Water 10-6 Amphoterism 10-7 Strengths of Acids 10-8 Acid-Base Reactions in Aqueous Solutions... 

The Swedish chemist Svante Arrhenius framed the first successful concept of acids and bases. He defined acids and bases in terms of the effect these substances have on water. According to Arrhenius, acids are substances that increase the concentration of H ion in aqueous solution, and bases increase the concentration of OH ion in aqueous solution. But many reactions that have characteristics of acid-base reactions in aqueous solution occur in other solvents or without a solvent. For example, hydrochloric acid reacts with aqueous ammonia, which in the Arrhenius view is a base because it increases the concentration of OH ion in aqueous solution. The reaction can be written... 

---