Acids and Bases
Acids and bases are two fundamental categories of chemical compounds. Acids are substances that donate protons, while bases are substances that accept protons. The strength of an acid or base is determined by its ability to donate or accept protons, respectively. These concepts are important in understanding chemical reactions and the behavior of substances in solution.
7 Key excerpts on "Acids and Bases"
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- 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- Tony Farine, Mark A. Foss(Authors)
- 2013(Publication Date)
- Routledge(Publisher)
...For this reason, the normal range of blood pH (7.35–7.45) is not as narrow as it first appears, and apparently small changes in blood pH represent large changes in hydrogen ion concentration, which you may need to report. Second, the pH scale is a negative scale – that is, a falling pH represents a rise in hydrogen ion concentration and a rising pH represents a falling hydrogen ion concentration. Pure water has a pH of 7 and an identical concentration of hydrogen ions and hydroxide ions, and therefore is referred to as neutral. If hydrogen ions are added, then [H + ] rises and pH falls – that is, acids have a pH of less than 7. In contrast, if hydrogen ions are removed, then [H + ] falls and pH rises – that is, bases have a pH of greater than 7. Salts as Acids and Bases When Acids and Bases react together, the salt (ionic compound) formed may be neutral, acidic or basic, depending on the strengths of the acid and base used in the reaction. If a strong acid is added to a strong base, or a weak acid is added to a weak base, then the resultant salt is neutral. In contrast, the reaction between a strong acid and a weak base results in the formation of an acidic salt, while the reaction between a weak acid and a strong base produces a basic salt. In-text review 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. A solution of an acid or base can be concentrated or dilute, irrespective of whether the acid or base is strong or weak. Acids and Bases react together to produce a salt and water. The concentration of hydrogen ions is described in terms of pH. Acid–base balance We have already looked at the concept of homeostasis in Chapter 2...
eBook - ePub- Jeffrey Gaffney, Nancy Marley(Authors)
- 2017(Publication Date)
- Elsevier(Publisher)
...Chapter 5 Acids and Bases Abstract This chapter explains the differences between the Brønsted-Lowry and Lewis definitions of Acids and Bases and gives examples of each. Since chemical reactions involving Lewis Acids and Bases are covered in more detail in Chapter 10, most of the chapter is dedicated to the applications of the Brønsted-Lowry concepts. This includes the strength of acids and their conjugate bases, the behavior of Acids and Bases in aqueous solution, the autoionization of water, and the acid ionization constants. The “p” functions, including pH, pOH, p K a, p K b, and p K w, are discussed. The function and uses of buffer solutions are explained along with their design using the Henderson-Hasselbalch equation. Titration procedures are discussed and their relevance to industrial situations is stressed. Keywords Brønsted-Lowry; Lewis acid; Conjugate pairs; Ionization constant; Amphoteric; Coordinate-covalent bond; Coordination complex; Buffer solution; Henderson-Hasselbalch; Titration Outline 5.1 Defining Acids and Bases 5.2 Acids and Bases in Aqueous Solution 5.3 The pH Scale 5.4 Other “p” Functions 5.5 Buffer Solutions 5.6 The Titration Important Terms Study Questions Problems 5.1 Defining Acids and Bases The first modern attempt at defining Acids and Bases was by a Swedish chemist named Svante Arrhenius in 1887. Arrhenius defined an acid as a material that releases hydrogen ions (H +) when dissolved in water. Similarly, he defined a base as a material that releases hydroxide ions (OH −) when dissolved in water. This definition only held for ionic compounds containing hydrogen or hydroxide ions and did not apply to many Acids and Bases that we deal with today. Since this early definition of Acids and Bases was so limited, two more sophisticated and general definitions of Acids and Bases have since been developed, which are in wide use today. These are known as the Brønsted-Lowry definition and the Lewis definition. In 1923, both J.N...
eBook - ePubFood Chemistry
A Laboratory Manual
- Dennis D. Miller, C. K. Yeung(Authors)
- 2022(Publication Date)
- Wiley(Publisher)
...1 Acids, Bases, and Buffers 1.1 Learning Outcomes After completing this exercise, students will be able to: Explain the roles of Acids and Bases in food products. Measure the pH of selected food products. Prepare and evaluate a buffer system. Measure the buffering capacity of a common beverage. 1.2 Introduction Many food components may be classified as acids or bases due to their capacity to donate or accept protons (hydrogen ions). These components perform numerous important functions including flavor enhancement, control of microbial growth, inhibition of browning, alteration of texture, prevention of lipid oxidation, and pH control. Acids and Bases are key metabolites in living plant and animal organisms, for example as intermediates in the TCA cycle, and are mostly retained when the plant is harvested or the animal is slaughtered so they are naturally present in foods. They may also be added during processing or synthesized during fermentation to produce desired characteristics in the final food product. The concentration and relative proportion of Acids and Bases determine the pH of a food, an extremely important characteristic. pH can affect the flavor, color, texture, stability, and behavior in food processing situations. For example, commercial sterilization of acid foods (pH less than 4.6) [1] can be achieved under milder processing conditions than in foods with a higher pH. 1.2.1 Acids Acids serve a variety of functions in foods including flavor enhancement, control of microbial growth, protein coagulation, emulsification, control of browning, buffering action, and metal chelation (to control lipid oxidation). All acids have a sour taste but different acids produce distinctively different sour flavors...
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...
eBook - ePub- J. G. Salway(Author)
- 2011(Publication Date)
- Wiley-Blackwell(Publisher)
...Part 1: Acids, bases and pH 1 Acids, bases and hydrogen ions (protons) Definition of PH pH is defined as “the negative logarithm to the base 10 of the hydrogen ion concentration”, For example, at pH 7.0, the hydrogen ion concentration is 0.000 000 1 mmoles/litre or 10 −7 mmol/l. Therefore, the negative log 10 is −(−7.0), i.e. +7.0 and hence the pH is 7.0. What Is PH? pH is “the “p ower of h ydrogen”. It represents “the negative logarithm 10 of the hydrogen ion concentration”. So why make things so complicated: why not use the plain and simple “hydrogen ion concentration”? Well, the concept was invented by a chemist for chemists and has advantages in chemistry laboratories. In clinical practice we are concerned with arterial values between pH 6.9 and 7.9. However, chemists need to span the entire range of pH values from pH 1 to pH 14. Values in terms of pH enable a convenient compression of numbers compared with the alternative which would be extremely wide-ranging as shown in Fig. 1.3...
