Properties of Acids and Bases

Common acids found in the laboratory include ethanoic acid, CH3COOH(aq), sulfuric acid, H2S04(aq), hydrochloric acid, HCl(aq), and nitric acid, HlSI03(aq). Acids are a group of compounds that exhibit the following properties when dissolved in water to form a dilute solution. 

Acids are electrolytes (Chapter 9), meaning they undergo chemical decomposition when an electric current is passed through their aqueous solutions. 

Apparatus for collecting the hydrogen produced by the reaction of zinc and hydrochloric acid 

The reaction between calcium carbonate and dilute hydrochloric acid 

The reaction between excess copper(ii) oxide and hydrochloric acid to form green copper(ii) chloride solution 

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Both of our explanations of the properties of acids and bases involve the hydrogen ion, H (aq). This species has great importance in the chemistry of aqueous solutions, so we shall consider what is known about it. 

The problem with the Arrhenius definitions is that they are specific to one particular solvent, water. When chemists studied nonaqueous solvents, such as liquid ammonia, they found that a number of substances showed the same pattern of acid-base behavior, but plainly the Arrhenius definitions could not be used. A major advance in our understanding of what it means to be an acid or a base came in 1923, when two chemists working independently, Thomas Lowry in England and Johannes Bronsted in Denmark, came up with the same idea. Their insight was to realize that the key process responsible for the properties of acids and bases was the transfer of a proton (a hydrogen ion) from one substance to another. The Bronsted-Lowry definition of acids and bases is as follows ... 

J 1 Describe the chemical properties of acids and bases (Section J.l). 

In the previous Sections, the properties of acids and bases in macrocycles and other concave structures have been compared. A number of factors have been recognized which influence the acidity or basicity of an acid or base (i) hydrogen bonds, (ii) hindered solvation (exclusion of solvent), (iii) formation of tight ion pairs (high microacidity but low overall acidity), and (iv) Coulomb forces when poly anions are formed. A fifth influence, (v) steric hindrance, still has to be discussed. 

Chemists use whatever tools they can find in their laboratories to take full advantage of the properties of acids and bases. One tool they use is Kipp s apparatus, a piece of laboratory equipment that relies on acid-base chemistry to do its job. Named for its inventor, Dutch pharmacist Petrus Johannes Kipp (1808-1864), Kipp s apparatus (or gas generator) is especially useful for creating gases, such as carbon dioxide, hydrogen, or hydrogen sulfide, that the chemists can then use in other chemical reactions. 

This approach explained many of the properties of acids and bases and many processes in which acids and bases appear, but not all (e.g. processes... 

In this chapter, you learned about solutions and how to use molarity to express the concentration of solutions. You also learned about electrolytes and nonelectrolytes. Using a set of solubility rules allows you to predict whether or not precipitation will occur if two solutions are mixed. You examined the properties of acids and bases and the neutralization reactions that occur between them. You then learned about redox reactions and how to use an activity table to predict redox reactions. You learned about writing net ionic equations. Finally, you learned how to use the technique of titrations to determine the concentration of an acid or base solution. 

Table 8.1 outlines properties of acids and bases that you have examined in previous courses. In this section, you will review two theories that help to explain these and other properties. As well, you will use your understanding of molecular structure to help you understand why acids and bases differ in strength. 

Table 8.1 Examples and Common Properties of Acids and Bases...

Relate the microscopic properties of acids and bases to their macroscopic properties. 

Imagine that you are asked to design a chemistry kit for young children to use. In one of the experiments, the properties of acids and bases are studied. What chemicals are appropriate for this experiment What safety precautions would you include ... 

Perhaps no two classes of compounds are more important in chemistry than acids and bases. All acids have several properties in common They have a sour taste, and they all react with most metals to form hydrogen gas (Hj) and with baking soda to form carbon dioxide (CO2). All acids turn blue litmus paper red, and their solutions conduct electricity because acids form ions when dissolved in water. t 11 bases also share several common properties They have a bitter taste, their solutions feel slippery like soapy water, and they turn red litmus paper blue (the opposite of acids). Solutions of bases also conduct electricity because they too form ions in water. Acids are similar because they produce hydrogen ion, (aq), in water. Bases, on the other hand, all form hydroxide ion, 0 [ (aq), in water. These ions are responsible for the properties of acids and bases. 

Each of the three definitions expands our concept of acids and bases. Arrhenius basic definition is adequate for understanding many of the properties of acids and bases. It is important to recognize, though, that acids and bases are not fixed labels that can be applied to a substance. Bronsted-Lowry and Lewis showed that acid-base characteristics are dependent on the reactions that take place between substances. A... 

Ohe pH of aqueous solutions—blood plasma, seawater, detergents, sap, and reaction mixtures—is controlled by the transfer of protons between water molecules and other molecules and ions. In Chapter 10, we learned about the properties of acids and bases. In this chapter, we see how to use solutions of weak acids or bases and their salts to maintain a desired pH. We also see how to identify the stoichiometric points of titrations. Finally, we meet the solubility equilibria that are the basis of qualitative analysis, the identification of the ions present in a sample. 

The characteristic properties of acids and bases have been known for centuries. Acids react with metals such as iron and zinc to yield H2 gas, and they change the color of the plant dye litmus from blue to red. By contrast, bases feel slippery, and they change the color of litmus from red to blue. When acids and bases are mixed in the right proportion, the characteristic acidic and basic properties disappear, and new substances known as salts are obtained. 

In this chapter, you will learn about the properties of acids and bases. You will learn how these properties change when acids and bases react together. As well, you will have a chance to estimate and measure the acidity of aqueous solutions. 

Table 10.2 on the next page summarizes the observable properties of acids and bases. These observable properties include their physical characteristics and their chemical behaviour. The Express Lab on page xxx provides you with an opportunity to compare some of these properties. What are acids and bases, however How does chemical composition determine whether a substance is acidic or basic You will consider one possible answer to this question starting on page 373. 

Studying acid-base properties of acids and bases, Pearson put forward the principle of hard and soft acids and bases according to which hard acids prefer to react with hard bases, while soft acids prefer to react with soft bases [12,13]. This principle has been widely used in chemistry, however, no quantitative characteristics of the hardness of acids and bases were known. 

It is useful to give a further discussion of acids and bases after the consideration of the basic principles of chemical equilibrium, because the phenomenon of chemical equilibrium is important in determining many of the properties of acids and bases. 

Another property of acid and base solutions is their ability to conduct electricity. Pure water is a nonconductor of electricity, but the addition of an acid or base to water causes the resulting solution to become a conductor. 

Properties of Acids and Bases in Aqueous Solutions The Brpnsted—Lowry... 

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