Acid-Base Chemistry Problems

All acid-base problems involving aqueous solutions of weak acids (HA) and/or their corresponding base forms (A-) fall into three distinct types type 1, Solutions of acid form only (e.g., HA) type 2, solutions of base form only (e.gM A-) type 3, solutions of both acid and base forms (e.g., HA and A ). For all three types of problems, two equilibrium conditions must be satisfied  

In solving any equilibria problems involving acids and bases, two terms must always be considered, charge-balance and mass-balance. To understand the use of these two terms, two examples are given below. 

Consider the addition of a small amount of a strong acid (e.g., 10-8 molL-1 HC1) to deionized water. Since hydrochloric acid is a strong acid, it completely dissociates to equamolar concentrations of H+ and Cl . The charge-balance term is 

Substituting the mass-balance term (Eq. F) into the charge-balance term (Eq. E) gives 

Equation G reveals that the concentration of H+ equals the concentration of HC1 plus OH contributed by H20. Therefore, 

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AQUEOUS SOLUTIONS AND ACID-BASE CHEMISTRY Problem 1-26... 

The polymer-supported catalysts are thus important conceptually in linking catalysis in solutions and catalysis on supports. The acid—base chemistry is fundamentally the same whether the catalytic groups are present in a solution or anchored to the support. The polymer-supported catalysts have replaced acid solutions in numerous processes because they minimise the corrosion, separation, and disposal problems posed by mineral acids. 

The first several chapters of any organic chemistry textbook focus on the structure of molecules how atoms connect to form bonds, how we draw those connections, the problems with our drawing methods, how we name molecules, what molecules look like in 3D, how molecules twist and bend in space, and so on. Only after gaining a clear understanding of stracture do we move on to reactions. But there seems to be one exception acid-base chemistry. 

So you only need one skill to completely master acid-base chemistry you need to be able to look at a negative charge and determine how stable that negative charge is. If you can do that, then acid-base chemistry will be a breeze for you. If you cannot determine charge stability, then you will have problems even after you finish acid-base chemistry. To predict reactions, you need to know what kind of charges are stable and what kind of charges are not stable. 

There are various definitions of acids and bases, and in discussing them it should be emphasized that the question is not one of validity but one of utility. Indeed, the problem of validity does not arise because of the fundamental nature of a definition. The problem is entirely one of choosing a definition which is of greatest use in the study of a particular field of acid-base chemistry. One point that needs to be borne in mind is that a concept of acids and bases is required that is neither too general nor too restrictive for the particular field of study. 

Ion pairing in acid-base systems. This problem incorporates ion-pair equilibria 13-12 and 13-13 into the acid-base chemistry of Section 13-1. 

Problems in this chapter include some brainbusters designed to bring together your knowledge of electrochemistry, chemical equilibrium, solubility, complex formation, and acid-base chemistry. They require you to find the equilibrium constant for a reaction that occurs in only one half-cell. The reaction of interest is not the net cell reaction and is not a redox reaction. Here is a good approach ... 

In summary, acid-base chemistry is conceptually rather simple, but the multiplicity of factors involved makes its treatment somewhat involved. Until more unifying concepts are developed, as they undoubtedly will be. it will be necessary to apply to each problem that is encountered the ideas, rules, and (when available) the parameters applicable to it. 

Additional aspects of the acid-base chemistry of amino acids and proteins are considered in Chapter 3, Section A and Chapter 6, Section E. The student may find it appropriate to study these sections at this time and to work the associated study problems. 

The key to solving acid-base equilibrium problems is to think about the chemistry—that is, to consider the possible proton-transfer reactions that can take place between Bronsted-Lowry acids and bases. 

Acid-base chemistry is central to many processes in oi ganic chemistry, so it has been a constant theme throughout this text. Tables 25.2 and 25.3 organize and summarize the acid-base principles discussed in Section 25.10. The principles in these tables can be used to determine the most basic site in a molecule that has more than one nitrogen atom, as shown in Sample Problem 25.4. 

Quantitative chemical analysis involves many types of ionic equilibria other than those between acids and bases, and the present chapter samples some of them. The formation of metal complexes takes place in homogeneous solution, and strongly resembles acid-base chemistry. In extraction, two different solvents are used, but both solutions are still homogeneous. Problems of solubility and precipitation involve two different physical forms of the compound of interest one dissolved, the other a solid phase. Electrochemical equilibria also involve at least two phases, of which one is an electronic conductor, typically a metal, and the other an ionic conductor such as an aqueous solution. Despite these differences in their physics, we will encounter much analogy in the mathematical description of these equilibria, which is why the present chapter is best read after chapter 4. 

Because acid-base reactions in solution generally are so rapid, we can concern ourselves primarily with the determination of species concentrations at equilibrium. Usually, we desire to know [H+], [OH ], and the concentration of the acid and its conjugate base that result when an acid or a base is added to water. As we shall see later in this text, acid-base equilibrium calculations are of central importance in the chemistry of natural waters and in water and wastewater treatment processes. The purpose of this section is to develop a general approach to the solution of acid-base equilibrium problems and to apply this approach to a variety of situations involving strong and weak acids and bases. 

Solve Because HF is a weak acid and HCl is a strong add, the major species in solution are HF, H, and Cl. The Cl, which is the conjugate base of a strong acid, is merely a spectator ion in any acid-base chemistry. The problem asks for [F ], which is formed by ionization of HF. Thus, the important equilibrium is HF(aq)... 

In certain contexts, the calculation of free energy differences is difficult to access computationally. Examples would include problems in which a large amount of solvent would need to be displaced in a chemical association, one in which a large conformational change occurs, or one in which a complex chemical intermediate is present. In these cases, one of which is described below in the context of acid-base chemistry, the method can often be readily combined with a hypothetical free energy cycle[46], with individual legs that are each readily evaluated computationally. 

Second, there is a problem of specificity. Suppose we want to make the trivial dipeptide Ala Leu. Even if we can avoid simple acid-base chemistry, random reaction between these two amino acids will give us at least the four possible dimeric molecules, and in practice, other larger peptides will be produced as well (Fig. 23.41). 

Heterogeneous catalytic reactions in a class of Alumino-Silicates called zeolites, is an area which has recently been shown to be amenable to a variety of Quantum Chemistry calculations. The present review is a short introduction to this field, focusing on the problem of proton transfer, the primary process central to the acid-base chemistry exhibited in the nanopores of zeolite. This problem is closely related to the controversial question of zeolite acidity that has evoked great interest both experimentally and theoretically. Recent ab initio results are compared with experiments and some of the difficulties associated with the use of Quantum Chemistry are discussed. Finally the future of such ab initio calculations are questioned in view of the growing developments in the application of First-Principles molecular dynamics to the study of such systems. 

New Tutorials cover critical content areas including acid-base chemistry and retrosynthetic analysis. These print tutorials are paired with MasteringChemistry online tutorials and can be used as additional problem sets that can be assigned as homework or test preparation. 

The problems of out-gassing are further illustrated when the essentially non-structural bonding of the satellite mirrors is considered. Here a silicone adhesive is used and, rather than using conventional acetic acid-based chemistry, which would fail the out-gassing criteria, oxime chemistry is employed. 

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