Acid-Base Reactions
Acid-base reactions involve the transfer of protons (H+) from an acid to a base. When an acid and a base react, they form water and a salt. Acids are substances that donate protons, while bases are substances that accept protons. This type of reaction is fundamental in understanding the behavior of many chemical compounds and is important in various industrial and biological processes.
7 Key excerpts on "Acid-Base Reactions"
eBook - ePub- Jean-Louis Burgot(Author)
- 2019(Publication Date)
- CRC Press(Publisher)
...Polyacids give several hydrated protons per molecule, while polybases give several hydroxide anions. The strengths of acids and bases are related to the extent of the ionization processes of reactions (140) and (141). Arrhenius’ theory only applies to aqueous solutions. It permits to correctly predict Acid-Base Reactions (in water) included from the quantitative standpoint. – According to Brönsted-Lowry’s theory, an acid HA is a proton donor: HA ⇌ A − + H + (145) A base B is a proton acceptor: B+H + ⇌ BH + (146) In these schemes, the symbol H + does not represent the naked proton. It represents the solvated proton in water. Within the framework of the theory, some authors prefer defining acids and bases after the following reactions (144) and (145). That is to say, the phenomena involve an exchange of protons with water according to: HA + H 2 O ⇌ A − + H 3 O + (147) B + H 3 O + ⇌ BH + + H 2 O (148) In (144), H 2 O (the solvent) also plays the part of a base. In (145), H 3 O + plays the part of an acid and H 2 O that of the solvent. According to this viewpoint, an acid-base reaction may be represented, in general, by the resultant of both Equations (144) and (145) : HA + B ⇌ A − + BH + (149) It appears that the acid-base reaction (146) can be split into the two half Acid-Base Reactions (144) and (145). Thus, an acid-base reaction involves an exchange of protons between two acid-base couples, HA/A − on one hand and, for example, the couple BH + /B on the other. It is interesting to notice that the proton exchange can be done not only directly between the members of the two pairs as indicated by reaction (146) but it can also be exchanged indirectly through the pair H 3 O + /H 2 O as indicated by reactions (144) and (145). It is also interesting to notice that half reactions (144) and (145) occur actually...
eBook - ePub- Jeffrey Gaffney, Nancy Marley(Authors)
- 2017(Publication Date)
- Elsevier(Publisher)
...So, there is an inverse relationship between the strength of an acid and the strength of its conjugate base, and likewise, there is an inverse relationship between the strength of a base and the strength of its conjugate acid. Strong acids produce weak conjugate bases and strong bases produce weak conjugate acids (see Table 5.1). Also, weak acids produce strong conjugate bases and weak bases produce strong conjugate acids. • Strong acid → Weak conjugate base • Strong base → Weak conjugate acid • Weak acid → Strong conjugate base • Weak base → Strong conjugate acid Since a weak acid has a weaker tendency to give up its proton and the conjugate base it produces has a stronger tendency to accept its proton, a competition results between the acid and the conjugate base for the proton. So, only a fraction of the weak acid molecules will donate a proton to the base, giving rise to a significant concentration of both the acid and conjugate base forms in solution. The reaction is said to be in chemical equilibrium, the state in which both reactants and products are present in concentrations which have no further tendency to change with time. This equilibrium is represented in the chemical equation by the presence of a double arrow between products and reactants, indicating that the reaction can go in both directions and both products and reactants are present; HA + B ⇌ A + HB The concentrations of all the species depend on the strengths of the acids and bases. The Brønsted-Lowry definition of acids and bases also describes more clearly what actually happens when an acid dissolves in water. From this point of view, the dissolution of acids, such as HCl, in aqueous solution is seen to involve an acid-base reaction between the acid and water. Although HCl is a covalent compound, it can donate a proton to a water molecule to form the cation H 3 O + ; HCl aq + H 2 O l → H 3 O + aq + Cl − aq The common name for this cation is the hydronium ion...
eBook - ePub- Tony Farine, Mark A. Foss(Authors)
- 2013(Publication Date)
- Routledge(Publisher)
...This was done so that acid–base imbalance, such as occurs in a variety of conditions, could be addressed. You will have noticed that on several occasions, reference was made to Chapter 2, since acid–base balance is very much concerned with regulating the normal internal environment. Summary points Acids are substances that donate hydrogen ions during a chemical reaction. Bases are substances that accept hydrogen ions during a chemical reaction. Acids and bases are described as weak or strong, depending upon the extent of their dissociation. Acids and bases react together to produce a salt and water. The concentration of hydrogen ions is described in terms of pH. A buffer is a solution that resists a change in pH. The body’s acid–base balance is maintained by buffer systems, respiratory regulation and renal regulation. Acid–base imbalances are either acidosis or alkalosis and may be described further as respiratory or metabolic. Self-test questions 1 Which one of the following acids does the stomach produce? (a) Citric acid. (b) Amino acid. (c) Hydrochloric acid. (d) Folic acid. 2 Which one of the following acids is not an important component of the diet? (a) Folic acid. (b) Amino acid. (c) Ascorbic acid. (d) Acetylsalicylic acid. 3 Which one of the following particles may also be referred to as a hydrogen ion? (a) An electron. (b) A...
eBook - ePub- Peter Kam, Ian Power(Authors)
- 2015(Publication Date)
- CRC Press(Publisher)
...Acids are removed from the body by lungs, kidneys and gastrointestinal tract. When an imbalance between the production and removal of H + ions occurs, the H + ion concentration deviates over a narrow range of 20–160 nmol/L (pH, 6.8–7.7). DEFINITIONS The hydrogen ion is a hydrogen atom without its orbital electron, and therefore it is a proton. In an aqueous solution, it exists as a hydrated proton called the hydronium ion (H 3 O +). • An acid is a substance that donates a proton. • A base is a substance that accepts protons in solution. In solution, an acid (HA) will dissociate to an H + ion and a base (A −), as shown in the following equation: HA ⇄ k 2 k 1 H + + A − The proportions of the relative reactions are determined by the dissociation constants k 1 and k 2. If k 1 is greater than k 2, then the reaction moves towards the production of H + and A −. Henderson applied the law of mass action and described the relationship as follows: [ H + ] = K [ HA ] A − where K = k 1 k 2 This shows that wthe concentration ([]) of H + ions in solution ([H + ]) depends on the ratio of the buffer pairs, A − and HA, and the dissociation constant. Hasselbach modified the Henderson equation using logarithmic transformation, resulting in the following equation: PH = p K a + log [ A − ] [ HA ] where pH is the logarithm of the hydrogen ion concentration and p K a is the negative logarithm of the dissociation constant of the substance and is the pH at which the substance is 50% dissociated. A substance with a lower p K a is a stronger acid than a substance with a higher p K a. The ability of a substance to donate or accept a proton (i.e., to act as an acid or a base) depends on the concentration of H + ions in solution (pH of the solution) and the degree of dissociation (p K) of the substance. P H SYSTEM H + ion concentration may be measured in two ways: directly as concentrations in nanomoles per litre or indirectly as pH...
eBook - ePub- Kevin R. Reel(Author)
- 2013(Publication Date)
- Research & Education Association(Publisher)
...CHAPTER 4 Types of Reactions CHAPTER 4 TYPES OF REACTIONS Acid-Base Reactions • Arrhenius Theory states that acids are substances that ionize in water to donate protons (H +), and bases produce hydroxide ions (OH −) when put into water. Example: Arrhenius acid: Arrhenius base: • Brønsted-Lowry Theory states that acids donate protons—like an Arrhenius acid—and bases accept protons. Simply put, a proton moves from one compound to another. Each compound in a conjugate acid-base pair is different from each other by the existence of a proton. Example: • Lewis Theory defines an acid as an electron-pair acceptor and a base as an electron-pair donor. The Lewis definition of Acid-Base Reactions allows the inclusion of reactions that may not involve protons, such as the formation of coordination complexes. Example: • Neutralization is the process where an Arrhenius acid and base are combined to form a salt and water. Example: • Amphoteric compounds can act as either acids or bases. Example: PRECIPITATION REACTIONS • Precipitation reactions occur when soluble reactants are mixed together to form an insoluble product, according to the solubility rules below. Example: • Precipitation reactions are best written as net ionic reactions, where only the ions that combine to form the precipitate are shown. All other ions that remain dissolved in solution are spectator ions. Example: Full equation: Net ionic reaction: Solubility Rules for Ions in Solution • All compounds with IA metals and ammonium are soluble. • All nitrates are soluble. • All chlorates and perchlorates are soluble. • All acetates are soluble. • All halides are soluble, EXCEPT those that combine with Ag +, Pb 2+, and Hg 2 2+. • All sulfates are soluble, EXCEPT those that combine with Ag +, Pb 2+, and Hg 2 2+, Ca 2+, Sr 2+, Ba 2+. • All hydroxides are insoluble, EXCEPT those with IA metals, ammonium, Ca 2+, Sr 2+, Ba 2+. • All carbonates are insoluble, EXCEPT those that contain IA metals and ammonium. •...
eBook - ePubChemistry
Concepts and Problems, A Self-Teaching Guide
- Richard Post, Chad Snyder, Clifford C. Houk(Authors)
- 2020(Publication Date)
- Jossey-Bass(Publisher)
...13 Acids and Bases Chapters 11 and 12 gave you an indication that all acids have certain properties in common and all bases have certain properties in common. The major common property is that acids react with bases (and vice versa) to produce salts. For example, if solutions of HCl (an acid) and KOH (a base) are mixed, the following reaction occurs. Such a reaction gives a solution that no longer has the acidic or basic properties that were evident before mixing, provided the correct volumes and concentrations were used. What then is an acid? What is a base? There are three definitions that have been developed through the years. Each has its own particular usefulness, depending upon the nature of the reactants and the conditions of the reaction. In this chapter we will discuss each of the definitions and their particular usefulness. Our discussion of acids and bases will touch on several other important concepts, including reactions of salts with water, another concentration term specially developed for acid–base solutions, and the importance of acid–base chemistry to physiological and industrial processes. OBJECTIVES After completing this chapter, you will be able to recognize and apply or illustrate the following: Arrhenius, Brønsted–Lowry, and Lewis acids and bases, neutralization, hydrolysis, pH, buffer solution, titration, conjugate acid or base, amphiprotic, indicator, hydronium ion, and hydrated; write a chemical equation for a neutralization reaction between any acid and base; predict whether a solution of a given salt will be acidic, basic, or neutral; calculate the pH of a solution when given: the degree of ionization of a weak acid or base and vice versa, K a or K b of the acid or base and vice versa, the concentration of a solution of a strong acid or base; solve titration problems. ARRHENIUS ACIDS AND BASES There are several chemical theories of acids and bases. The most familiar is that of Arrhenius...
eBook - ePub- Professor Rob Beynon, J Easterby(Authors)
- 2004(Publication Date)
- Taylor & Francis(Publisher)
...Under physiological conditions, the species on both sides of the equation can co-exist in substantial amounts—compare this with a strong acid such as HCl, which is virtually completely ionized to H + and Cl –. There are other more rigorous definitions of weak acids and bases which were alluded to in Chapter 2, but these need not concern us here. ◊ Nearly all pH buffers are weak acids or bases. Notice that the weak acid can be neutral (acetic acid) or carry a positive (TrisH +) or negative (phosphate 1–) charge. As we develop the theory of buffers, it will become clear that these charges on the buffer species have important consequences. 2. Weak acids and bases resist pH changes A buffer is able to resist changes in pH because it exists in an equilibrium between a form that has a hydrogen ion bound (conjugate acid, protonated) and a form that has lost its hydrogen ion (conjugate base, deprotonated). For the simple example of acetic acid, the equation is: CH 3 COOH ⇌ CH 3 COO − + H + Here, the protonated form is acetic acid, with a net charge of zero, whereas the deprotonated form (acetate) has a charge of −1. The two species are in equilibrium, and this equilibrium, in common with all equilibria, can be displaced by addition of one component. Consider a solution that contains equal amounts of acetic acid and acetate ions (10 mM acetic acid, 10 mM sodium acetate, for example). If we were to add a strong acid, such as HCl, to this solution, the added H + would displace the equilibrium to the left. Binding of H + to CH 3 COO – ‘mops up’ the added protons (Figure 3.1). Electrical neutrality is preserved because every H + that reacts with a CH 3 COO – anion to form the neutral CH 3 COOH leaves behind a chloride (Cl –) anion in its place. Add a strong base, such as sodium hydroxide, and the OH - ion would react with the H + and displace the equilibrium to the right...
