Chemistry
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.
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11 Key excerpts on "Acids and Bases"
eBook - PDF- Ageetha Vanamudan(Author)
- 2023(Publication Date)
- Delve Publishing(Publisher)
In this part, we’ll take a short look at each of Introduction to Molecular Science 222 them. Acids and Bases can be described using one of the three principles listed below: In acidic solutions, there are two types of H + ions: those produced by acid and those produced by an alkaline solution. According to Bronsted and Lowry, an acid is a proton donor, and a base is an acceptor. For Acids and Bases, there exist “electron acceptors” and “electron donors,” as described by Lewis. 13.5.2 The Theory of Acids and Bases by Arrhenius According to the Arrhenius hypothesis, the H + ion is generated when acid is dissolved in water. The solution’s H + ion concentration increases. When the base is dissolved in water, it ionizes the OH - ion. As a result, the solution contains a lot of OH - ions. Arrhenius acid can be used to enhance the concentration of protons or H + ions in an aqueous solution (Kharat et al., 2017). Figure 13.6: Nitric acid in a chemical bottle. Source: https://media.istockphoto.com/photos/nitric-acid-in-glass-chemical- in-the-laboratory-picture-id1350071266?k=20&m=1350071266&s=612x612 &w=0&h=pqe5b9pVKlFszNzjoPUGXnIXMeIMCUK_qzXKRcnPq5k= 13.5.3 Arrhenius Acids Svante Arrhenius, a Swedish scientist, proposed the Arrhenius theory of Acids and Bases in 1884. According to his concept, Acids and Bases should be categorized based on the type of ions they produce when dissolved in water (O’Gorman et al., 2012). For example, a hydrochloric acid solution in water. To summarize, HCl degrades into H + and Cl – . The production of hydronium ions raises the concentration of H + ions. Acids and Bases 223 H+ (aq) + aqueous HCl (aq) In the lab, HCl (aq) + H 2 O (l) = H 3 O+ (aq) + Cl - (aq) 13.5.4 Arrhenius base To increase the concentration of water-soluble hydroxide ions in a solution, substances such as an Arrhenius base are utilized. The material must be both water-soluble and capable of dissociating into sodium and hydroxide ions to be classified as an Arrhenius base.
- Peter V. Hobbs(Author)
- 2000(Publication Date)
- Cambridge University Press(Publisher)
5 Acids and Bases Very early in the history of chemistry many substances were designated as acids, bases, and salts. Acids have a sour taste (e.g., citric acid gives lemon juice its sour taste); they dissolve certain metals; and they also dissolve carbonate minerals to produce carbon dioxide. Bases have a bitter taste (e.g., sodium carbonate); they feel slippery when touched; and they react with many dissolved metal salts to form precipitates. However, the most striking characteristic of bases is their ability to neutralize the properties of acids; when a base reacts with an acid a salt is produced. The French chemist Lavoisier thought that all acids contain oxygen (the word oxygen means acid former in Greek). However, it was sub-sequently found that many acids contain no oxygen (e.g., hydrochloric acid, HC1), but that they all contain hydrogen. Acids and Bases figure prominently in the equilibrium of aqueous solu-tions, where they significantly enhance the electrical conductivity of water. In this chapter, we will explore some of the important properties of Acids and Bases in aqueous solutions. This will lead us to a discussion of several theories of Acids and Bases. 5.1 Some definitions and concepts Equation (4.22) is valid for aqueous solutions as well as for pure water. A solution for which [H + (aq)] = [OH~(aq)] is said to be neutral; thus, pure water is neutral. If [H + (aq)] > [OH~(aq)] the solution is said to be acidic. If [OH(aq)] > [H + (aq)] the solution is said to be basic. Exercise 5.1. If 0.02 mole of hydrochloric acid is dissolved in 1L 1 of water, what are the concentrations of H + (aq) and OH(aq) ions I in the solution at 25°C? I 83 84 Acids and Bases Solution. Hydrochloric acid is a gas under normal conditions, but it is a strong electrolyte that dissolves in water to form equal numbers of H + (aq) and Q(aq).
eBook - PDF- Allan Blackman, Steven E. Bottle, Siegbert Schmid, Mauro Mocerino, Uta Wille(Authors)
- 2022(Publication Date)
- Wiley(Publisher)
The reaction of water with itself represents arguably the simplest example of such a reaction. In this case, water acts as both an acid and a base. The concept of Acids and Bases has been known for hun- dreds of years, but it is only relatively recently that def- initions of the words ‘acid’ and ‘base’ have been agreed upon. The word acid derives from the Latin acidus, mean- ing sour; acids do indeed taste sour, but it is not a good idea to taste them in the laboratory. The word alkali, which is synonymous with base, comes from the Arabic al-qaliy, literally ‘the ashes’, referring to the ashes of the salt- wort plant that grows in alkaline soils. The first comprehensive theory concerning Acids and Bases appeared in 1884 in the PhD thesis of the Swedish chemist, Svante Arrhenius (1859– 1927; Nobel Prize in chemistry, 1903; figure 11.2), who was nearly failed for proposing that ions could exist in solution. He defined an acid as a substance that released H + ions when dissolved in water, and a base as a substance that gave rise to OH - ions on dissolution in water. This definition is similar to the more general Brønsted–Lowry definition of Acids and Bases, which we will use from this point. This was proposed by Johannes Brønsted, a Danish chemist, and Thomas Lowry, an English chemist, independently of each other in 1923. They considered that acid–base reactions involved proton (H + ) transfer between an acid and a base, which they defined as follows. FIGURE 11.2 Svante Arrhenius proposed the first comprehensive theory of Acids and Bases. • An acid is a proton donor. • A base is a proton acceptor. CHAPTER 11 Acids and Bases 499 In other words, a Brønsted–Lowry acid will donate a proton to a Brønsted–Lowry base, which will accept it. From now on, we will refer to Brønsted–Lowry Acids and Bases simply as Acids and Bases. To illustrate the Brønsted–Lowry concept, let’s return to the example involving water that we introduced previously.
eBook - PDFChemistry
Structure and Dynamics
- James N. Spencer, George M. Bodner, Lyman H. Rickard(Authors)
- 2011(Publication Date)
- Wiley(Publisher)
468 Chapter Eleven Acids and Bases 11.1 Properties of Acids and Bases 11.2 The Arrhenius Definition of Acids and Bases 11.3 The Brønsted–Lowry Definition of Acids and Bases 11.4 Conjugate Acid–Base Pairs 11.5 The Role of Water in the Brønsted Model 11.6 To What Extent Does Water Dissociate to Form Ions? 11.7 pH as a Measure of the Concentration of the H 3 O Ion 11.8 Relative Strengths of Acids and Bases 11.9 Relative Strengths of Conjugate Acid–Base Pairs 11.10 Relative Strengths of Different Acids and Bases 11.11 Relationship of Structure to Relative Strengths of Acids and Bases 11.12 Strong Acid pH Calculations 11.13 Weak Acid pH Calculations 11.14 Base pH Calculations 11.15 Mixtures of Acids and Bases: Buffers 11.16 Buffers and Buffer Capacity 11.17 Buffers in the Body 11.18 Acid–Base Reactions 11.19 pH Titration Curves Special Topics 11A.1 Diprotic Acids 11A.2 Diprotic Bases 11A.3 Compounds That Could Be Either Acids or Bases 11.1 Properties of Acids and Bases For more than 300 years, chemists have classified substances that behave like vinegar as acids and substances that have properties like wood ash as bases (or alkalies). The word acid comes from the Latin acidus, which means “sour,” and refers to the sharp odor and sour taste of many acids. Vinegar, for example, tastes sour because it is a dilute solution of acetic acid in water. Lemon juice tastes sour because it contains citric acid. Milk turns sour when it spoils because lactic acid is formed, and the unpleasant, sour odor of rotten meat or butter can be attrib- uted to compounds such as butyric acid that form when fat spoils. One of the characteristic properties of an acid is its ability to dissolve most metals. Zinc metal, for example, rapidly reacts with hydrochloric acid to form an aqueous solution of ZnCl 2 and hydrogen gas. Another characteristic property of acids is their ability to change the color of veg- etable dyes such as litmus.
eBook - PDF- Leo J. Malone, Theodore O. Dolter(Authors)
- 2012(Publication Date)
- Wiley(Publisher)
SETTING A GOAL ■ ■ You will expand your knowledge of Acids and Bases with more general definitions that allow us to examine their comparative strengths. Part A Acids, Bases, and the Formation of Salts 13-1 Properties of Acids and Bases LOOKING AHEAD! Historically, well before scientists knew much about their composi- tions, Acids and Bases were classified as such based on their common properties. These common properties relate to a specific “active ingredient.” The nature of these properties and the active ingredients are the topics of this section. ■ The sour taste of acids accounts for the origin of the word itself. The word acid originates from the Latin acidus, meaning “sour,” or the closely related Latin acetum, meaning “vinegar.” This ancient class of compounds has several characteristic chemi- cal properties. Acids are compounds that do the following: 1. Taste sour (of course, one never tastes laboratory chemicals) 2. React with certain metals (e.g., Zn and Fe), with the liberation of hydrogen gas (see Figure 13-1) 3. Cause certain organic dyes to change color (e.g., litmus paper turns from blue to red in acids) 4. React with limestone (CaCO 3 ), with the liberation of carbon dioxide gas (see Figure 13-1) 5. React with bases to form salts and water Some familiar acids, their common names, and their formulas are shown below. CHEMICAL NAME COMMON NAME FORMULA hydrochloric acid muriatic acid HCl sulfuric acid oil of vitriol, battery acid H 2 SO 4 acetic acid vinegar (sour ingredient) HC 2 H 3 O 2 carbonic acid carbonated water H 2 CO 3 The counterparts to acids are bases. Bases are compounds that do the following: 1. Taste bitter 2. Feel slippery or soapy 3. Dissolve oils and grease 4. Cause certain organic dyes to change color (e.g., litmus paper turns from red to blue in bases) 5. React with acids to form salts and water C C OBJECTIVE FOR SECTION 13-1 List the general properties of Acids and Bases.
eBook - PDF- Douglas P. Heller, Carl H. Snyder(Authors)
- 2015(Publication Date)
- Wiley(Publisher)
For example, hydrochloric acid (HCl) and acetic acid (CH 3 CO 2 H) are acids, whereas ammonia (NH 3 ) is not. • Ionic compounds containing the hydrox- ide ion (OH − ) or carbonate ion (CO 3 2− ) are basic; examples are sodium hydroxide (NaOH) and calcium carbonate (CaCO 3 ). Other kinds of compounds, without OH − or CO 3 2− ions, can also be basic. The covalent compound ammonia (NH 3 ) for example, is a common base. We will explore the reasons behind these ob- servations shortly. 8.1 Acids, Bases, and Neutralization LEARNING OBJECTIVES 1. Describe three simple ways to distinguish between Acids and Bases. 2. Explain acid-base neutralization. 3. Define Acids and Bases at the molecular level. hen you bite into a lemon or other citrus fruit, you experience the familiar sour taste of acids. On the other hand, if you’ve ever tasted a pinch of baking soda or had the misfortune of getting soap in your mouth, you have ex- perienced the bitter flavor of bases. We’ll elaborate on simple observations such as these that help us differen- tiate between Acids and Bases. Then we will explore the molecular basis for why these two classes of compounds behave as they do. Acids and Bases—Preliminary Observations A sour taste, in fact, may be the earliest known test for acidity. Our word acid comes from the Latin acidus, an adjective meaning “sour” or “having a sharp taste.” In addition, we know that water solutions of acids: • turn litmus paper red and • react with certain metals, such as magnesium, or zinc, to liberate hydrogen gas (Figure 8.1). In addition to tasting bitter, water solutions of all bases: • turn litmus paper blue and • feel slippery. Of all these diagnostic tests, only the litmus test is safe enough for general use with a substance of un- certain identity. It is far too dangerous to taste a substance you’re not sure of or to rub it between your fingers to learn whether it has the proper- ties of an acid or a base.
eBook - PDFChemistry
The Molecular Nature of Matter
- Neil D. Jespersen, Alison Hyslop(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
1. Take notes in class and when you read the chapter. Notes are messy, full of questions, have diagrams and pictures, include your reactions to the material, and draw connections between concepts. Sometimes they even include doodles. 2. Choose two concepts from the chapter and prepare a lesson to teach the material to someone else. Then present the lesson. 3. Choose two concepts that you find confusing from this chapter, and ask your profes- sor, TA, or classmate to explain them. If you still are confused about the concepts, ask another person for help. 15.1 Brønsted–Lowry Acids and Bases In Chapter 4, an acid was described as a substance that produces H 3 O + in water, whereas a base gives OH − . An acid–base neutralization reaction, according to Arrhenius, occurs when an acid and a base combine to produce water and a salt. However, many reactions resemble neutralizations without involving H 3 O + , OH − , or even H 2 O. For example, when open bottles of concentrated hydrochloric acid and concentrated aqueous ammonia are placed side by side, a white cloud forms when the vapors from the two bottles mix (see Figure 15.1). The cloud consists of tiny crystals of ammonium chloride, which form when ammonia and hydrogen chloride gases, escaping from the open bottles, mix in air and react. NH 3 (g) + HCl(g) ⟶ NH 4 Cl(s) What’s interesting is that this is the same net reaction that occurs when an aqueous solution of ammonia (a base) is neutralized by an aqueous solution of hydrogen chloride (an acid). Yet, the gaseous reaction doesn’t fit the description of an acid–base neutralization according to the Arrhenius definition because there’s no water involved. If we look at both the aqueous and gaseous reactions, they do have something in common. Both involve the transfer of a proton (a hydrogen ion, H + ) from one particle to another. 1 In water, where HCl is completely ionized, the transfer is from H 3 O + to NH 3 , as we discussed in Section 4.6.
- Frederick Bettelheim, William Brown, Mary Campbell, Shawn Farrell(Authors)
- 2019(Publication Date)
- Cengage Learning EMEA(Publisher)
240 | Chapter 8 Acids and Bases Copyright 2020 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 8.6 Properties of Acids and Bases Today’s chemists do not taste the substances they work with, but 200 years ago they routinely did so. That is how we know that acids taste sour and bases taste bitter. The sour taste of lemons, vinegar, and many other foods, for example, is due to the acids they contain. A. Neutralization The most important reaction of Acids and Bases is that they react with each other in a process called neutralization. This name is appropriate be-cause, when a strong corrosive acid such as hydrochloric acid reacts with a strong caustic base such as sodium hydroxide, the product (a solution of ordinary table salt in water) has neither acidic nor basic properties. We call such a solution neutral. Section 8.9 discusses neutralization reactions in detail. B. Reaction with Metals Strong acids react with certain metals (called active metals) to produce hydrogen gas, H 2 , and a salt. Hydrochloric acid, for example, reacts with magnesium metal to give the salt magnesium chloride and hydrogen gas ( Figure 8.1 ). 1 Mg( s ) Magnesium MgCl 2 ( aq ) Magnesium chloride H 2 ( g ) Hydrogen 2HCl( aq ) Hydrochloric acid 1 The reaction of an acid with an active metal to give a salt and hydrogen gas is a redox reaction (Section 4.4). Both the acid and the salt formed are ion-ized in aqueous solution.
eBook - PDF- David Ucko(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
base (excess O H ions) 0 Concentration in moles per liter (molarity). e a ds and ases T h e acidity or basicity (alkalinity) of a substance depends on two factors—its solubility in water and its ability to ionize in solution. Neither of these taken alone, the concentration or the degree of dissociation, gives you enough infor-mation. For example, acetic acid is extremely soluble in water and solutions having a high concentration can b e prepared. These solutions are weakly acidic, however, because only a small fraction of the molecules dissociate. O n the other hand, magnesium hydroxide is a base that dissociates almost c o m -pletely in water. Yet only a small amount of hydroxide ions is present because relatively little of the solid base can b e dissolved. An acid is strong if the solution contains a large excess of hydrogen ions and a base is strong if the solution contains a large excess of hydroxide ions. T h e concentration of hydrogen ion and of hydroxide ion, and therefore the strength of an acid or base, is expressed by a quantity known as p H . T h e p H of a solution is a direct measure of the concentration of hydrogen (or hy-dronium) ions in solution; it is a scale running from 0, strong acid, to 14, strong base, in water. T h e midpoint, p H 7, represents a neutral solution, neither acidic nor basic, because the concentrations of H + and O H ~ are equal. Table 8-4 illustrates the meaning of the p H scale; concentrations are given in terms of moles per liter. 8.5 e a ds and ases Pure water is neutral; both the hydrogen ion concentration and the hy-droxide ion concentration are 0.0000001 (10~ 7 ) mole/liter. An acid solution has a greater hydrogen ion concentration and smaller hydroxide ion concentration than pure water; its p H is less than 7. T h e more hydrogen ions present, the more acidic the solution and the lower its p H .
eBook - PDFChemistry for Today
General, Organic, and Biochemistry
- Spencer Seager, Michael Slabaugh, Maren Hansen, , Spencer Seager, Spencer Seager, Michael Slabaugh, Maren Hansen(Authors)
- 2021(Publication Date)
- Cengage Learning EMEA(Publisher)
Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Acids, Bases, and Salts 281 9.9 The Strengths of Acids and Bases Learning Objective 9 Demonstrate an understanding of the words weak and strong as applied to Acids and Bases. When salts dissolve in water, they generally dissociate completely, but this is not true for all Acids and Bases. The Acids and Bases that do dissociate almost completely are classified as strong acids and strong bases (they are also strong electrolytes). Those that dissociate to a much smaller extent are called weak or moderately weak, depending on the degree of dissociation (they are also weak or moderately weak electrolytes). Examples of strong and weak acids are given in Table 9.7. strong acids and strong bases Acids and Bases that dissociate (ionize) completely when dissolved to form a solution. weak (or moderately weak) Acids and Bases Acids and Bases that dissociate (ionize) less than completely when dissolved to form a solution. TABLE 9.7 Some Common Strong and Weak Acids Name Formula % Dissociation a K a Classification Hydrochloric acid HCl 100 Very large Strong Hydrobromic acid HBr 100 Very large Strong Nitric acid HNO 3 100 Very large Strong Sulfuric acid H 2 SO 4 100 Very large Strong Phosphoric acid H 3 PO 4 28 7.5 3 10 23 Moderately weak Sulfurous acid b H 2 SO 3 34 1.5 3 10 22 Moderately weak Acetic acid HC 2 H 3 O 2 1.3 1.8 3 10 25 Weak Boric acid H 3 BO 3 0.01 7.3 3 10 210 Weak Carbonic acid b H 2 CO 3 0.2 4.3 3 10 27 Weak Nitrous acid b HNO 2 6.7 4.6 3 10 24 Weak a Based on dissociation of one proton in 0.1 M solution at 25°C.
eBook - PDF- David R. Klein(Author)
- 2020(Publication Date)
- Wiley(Publisher)
When mixed with water, the acid and the base can react with each other, ultimately producing CO 2 : H + CO 2 H 2 O Sodium bicarbonate Carbonic acid Potassium bitartrate O HO Na O O OH OH O K HO O OH + Na OH OH O O K ⊕ ⊕ ⊕ ⊕ O ⊝ O ⊝ ⊝ O O ⊝ Baking powder is often used when making pancakes, muffins, and waffles. It is an essential ingredient in the recipe if you want your pancakes to be fluffy. In any recipe, the exact ratio of acid and base is important. Excess base (sodium bicarbonate) will impart a bitter taste, while excess acid will impart a sour taste. In order to get the ratio just right, a recipe will often call for some specific amount of baking soda and some specific amount of baking pow- der. The recipe is taking into account the amount of acidic compounds present in the other ingredients, so that the final product will not be unnecessarily bitter or sour. Baking is truly a science! mpart a sour o just right, a specific some w - 122 CHAPTER 3 Acids and Bases HCl is an acid according to either definition. It is a Lewis acid because it serves as an electron-pair acceptor, and it is a Brønsted-Lowry acid because it serves as a proton donor. But the Lewis defini- tion is an expanded definition of Acids and Bases, because it includes reagents that would otherwise not be classified as acids or bases. For example, consider the following reaction: H H H H B B F F F F F F + Base (electron-pair donor) Acid (electron-pair acceptor) O ⊝ ⊕ O According to the Brønsted-Lowry definition, BF 3 is not considered an acid because it is has no protons and cannot serve as a proton donor. However, according to the Lewis definition, BF 3 can serve as an electron-pair acceptor, and it is therefore a Lewis acid. In this reaction, H 2 O is a Lewis base because it serves as an electron-pair donor. Take special notice of the curved-arrow notation. There is only one curved arrow in the reaction above, not two.
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