Acids and Bases in Chemistry

When placed in water, some acids and bases completely ionize, or dissociate into their ions—but others do not. Acids and bases that completely ionize are called strong acids and strong bases. Strong acids are defined as acids that have a pH of 0-4. Strong bases have pH values of 10-14. On the other hand, weak acids and weak bases do not disassociate completely in water. This leads to a pH value that is closer to neutral, because some of the hydrogen ions are still attached to other atoms, decreasing the hydrogen ion concentration. 

The breakdown of any acid or base in water to form its ions is a reversible reaction. Hydrochloric acid, for example, is a strong acid that dissociates completely to form hydrogen ions and chlorine ions  

In a weak acid or base, the backwards reaction (where ions join to form the acid or base) occurs more often than it does in a strong acid or base. Therefore, with a weak acid or base, some hydrogen and hydroxide ions are released, but there are many more molecules of intact acid or base than there would be with a strong acid or base. Most acids and bases are weak. They do not completely break down in water. 

Chemists have calculated the extent to which most acids and bases will dissociate in water. This mathematical value is called the acid dissociation constant (Ka) for acids and the base dissociation constant (Kb) for bases. The higher the value for Ka or Kb, the more the acid or base dissociates in water and the stronger it is. 

Hydrochloric acid has the highest Ka on this list and is, therefore, the strongest acid listed. Lithium hydroxide is the strongest base listed. Because Ka and Kb values are often very large or very small numbers, chemists have converted them into an easier form called pKa and pKb. 

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Taking a closer look at the aspects of an activity that may have the power to enhance positive student affect, a variety of facets have to be considered it might be the underlying content of the task (e.g., acids and bases in chemistry), the embeddedness of the topic (e.g., task situation), the social mode (e.g., group activity), the openness of the task (e.g., inquiry-based), or the fit of the task difficulty to student competence (e.g., adaptation to student needs). Thus, it is necessary to describe the concrete situation in which learning takes place. According to Finkelstein (2005), three levels of context have to be clearly differentiated in science education in order to avoid confusion of terms the task... 

In the Preface we postponed a more detailed discussion of the real function of the electronic theory of acids and bases in chemistry until now. More discussion of the theory itself was necessary before its significance could be presented. 

R. G. Pearson, J. Am. Chem. Soc. 85 3533 (1963) T. L. Ho, Hard and Soft Acids and Bases in Organic Chemistry, Academic Press, New York, 1977 W. B. Jensen, The Lewis Acid-Base Concept, Wiley-Interscience, New York, 1980, Chapter 8. 

New Chapter 1 has been retitled Structure Determines Properties to better reflect its purpose and has been rewritten to feature a detailed treatment of acids and bases. Rather than a review of what students learned about acids and bases in general chemistry. Sections 1.12-1.17 discuss acids and bases from an organic chemistry perspective. 

A. HuLANlCKl, Reactions of Acids and Bases in Analytical Chemistry, Ellis Horwood (Wiley), Chichester, 1987, 308 pp. 

Any reaction in which a proton is transferred from one substance to another is an acid-base reaction. More specifically, the proton-transfer view is known as the Bronsted-Lowiy definition of acids and bases. In an acid-base reaction, an acid donates a proton, and a base accepts that proton. Any species that can give up a proton to another substance is an acid, and any substance that can accept a proton from another substance is a base. The production of two water molecules from a hydroxide anion (a base) and a hydronium ion (an acid) is just one example of an acid-base reaction acids and bases are abundant in chemistry. 

You learned about acids and bases in your previous chemistry course. In this chapter, you will extend your knowledge to learn how the structure of a compound determines whether it is an acid or a base. You will use the equilibrium constant of the reaction of an acid or base with water to determine whether the acid or base is strong or weak. You will apply your understanding of dissociation and pH to investigate buffer solutions solutions that resist changes in pH. Finally, you will examine acid-base titrations that involve combinations of strong and weak acids and bases. 

Long. F.A., and R.H. Bovd Acid and Bases, in McGraw-Hill Encyclopedia of Chemistry, McGraw-Hill Companies. Inc, New York, NY. 1983. 

Titration is one of the universal techniques of chemistry and is commonly used to determine the concentration of a solute. Titrations may be either acid-base titrations, in which an acid reacts with a base, or redox titrations, in which the reaction is between a reducing agent and an oxidizing agent. Here we concentrate on acid-base titrations. The technique is used in research laboratories, hospitals, and industry to determine the amounts of acid and base in solutions. It is also used in forensic laboratories and for monitoring the environment. 

The discussion of acids and bases in the previous section helps us understand the chemistry of the Grignard reagents. Grignard reagents are made by reacting an alkyl bromide with magnesium metal in diethyl ether. 

Refs. [i] Todd JF (1991) Pure Appl Chem 63 1541 [ii] Dissociation constants of inorganic acids and bases. In Lide DR (ed) (2003) CRC handbook of chemistry and physics, 84th edn. CRCPress, Boca Raton, pp 8-44 - 8-45 [Hi] Dissociation constants of organic acids and bases. In Lide DR (ed) (2003) CRC handbook of chemistry and physics, 84tn edn. CRC... 

In this section, you applied your understanding of aqueous solutions to explore the chemistry of water quality. Some of the chemicals you considered belong to a group of compounds that are called acids and bases. In the next chapter, you will investigate the properties and chemical behaviour of these important compounds. 

The HCl separates to form H+ and Ch. Ionization in water will be discussed with the chemistry of acids and bases in Chapter 9. 

The degree of dissociation, or strength, of acids and bases has a profound influence on their aqueous chemistry. For example, vinegar (a 5% [w/v] solution of acetic acid in water) is a consumable product aqueous hydrochloric acid in water is not. Why Acetic acid is a weak acid and, as a result, a dilute solution does no damage to the mouth and esophagus. The following section looks at the strength of acids and bases in solution in more detail. 

Another important drug physicochemical phenomenon is the ionization of Bronsted acids and bases in aqueous solution that plays a central role in much of chemistry and biochemistry and that also affects drug in vitro stability and in vivo metabolism activity. The extent of ionization can be represented by the pKg or ionization constant, which often is used in predicting drug-drug interaction because of the change of acid or base properties. For example, given a weak acid HA, its dissociation in water is subject to the chemical equilibrium ... 

Biochemists usually discuss acids and bases in terms of their ability to donate and accept protons that is, they use the Brpnsted definition of acids and bases. A few concepts from general chemistry are important to help organize your thoughts about biochemical acids and bases ... 

Each of the contexts discussed above has left its marks on the chapter on acids and bases in most general chemistry textbooks, for example, in Chemie (1998), which is the most commonly used textbook for secondary education in the Netherlands. The chapter starts with an every day context tasting acids. Within the next two sentences the acid is subsequently a solution (vinegar), a substance (acetic acid), a solution of the substance (a certain concentration of acetic acid in water). The text continues by explaining the pH scale, and switches in the next sections to describe an acid as a particle, from which a proton can be removed. These examples show that the coherence within the chapter is rather problematic. Its structure is not a result of a well thought out pedagogical strategy. Instead, it is a... 

Non-aqueous acid-base systems Water plays a crucial role in the acid-base chemistry of aqueous solutions, but in the absence of water it is possible to have other families of acids and bases in which different solvents play a role analogous to that of water. Perhaps the most common of these is the liquid ammonia system . Like water, NH3 is amphiprotic and can engage in autoprotolj is ... 

So ubiquitous is water on this planet that ourview of chemistry, by custom and convenience, is strongly biased in favour of aqueous solutions. What then are we to make of other solvents where the strongest acid may be the least ionised, where a respectable acid like CH3CO2H behaves as a base, where an anion base achieves stabilisation only by bonding to a molecule of its conjugate acid Examination of acids and bases in non-aqueous solvents cannot fail to be enlightening. 

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