Concepts Of Acids And Bases Pdf
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This page describes the Arrhenius, Bronsted-Lowry, and Lewis theories of acids and bases, and explains the relationships between them. It also explains the concept of a conjugate pair - an acid and its conjugate base, or a base and its conjugate acid. The Arrhenius theory is of historical interest only, and you are unlikely to need it unless you are doing some work on the development of ideas in chemistry.
Chapter 12 — Acid-Base Chemistry Introduction The terms acid and base have been used for several hundred years. Acids were substances that had a sour taste, were corrosive, and reacted with substances called bases.
This theory is a generalization of the Arrhenius theory. The definition is expressed in terms of an equilibrium expression. Most acid-base reactions are fast so that the components of the reaction are usually in dynamic equilibrium with each other. The reverse of an acid-base reaction is also an acid-base reaction, between the conjugate acid of the base in the first reaction and the conjugate base of the acid. In the above example, acetate is the base of the reverse reaction and hydronium ion is the acid.
Arrhenius Acid-Base Theory
In G. In the Lewis theory of acid-base reactions, bases donate pairs of electrons and acids accept pairs of electrons. In other words, a Lewis acid is an electron-pair acceptor. A Lewis base is any substance, such as the OH - ion, that can donate a pair of nonbonding electrons. A Lewis base is therefore an electron-pair donor. One advantage of the Lewis theory is the way it complements the model of oxidation-reduction reactions.
Classical concept of acids and bases. Acid is a substance whose aqueous solution possessed the following characteristic properties. Base is a substance whose aqueous solution possessed the following characteristic properties:. Arrhenius in put forward a theory popularly known as Arrhenius theory of ionization. When an electrolyte is dissolved in water ,it dissociates into positively and negatively charged ions. Such acids are called strong acids.
There are three major classifications of substances known as acids or bases. This theory was developed by Svante Arrhenius in Later, two more sophisticated and general theories were proposed. The Lewis theory is discussed elsewhere. In , the Swedish chemist Svante Arrhenius proposed two specific classifications of compounds; acids and bases.
Concepts of Acids and Bases
Acids have long been recognized as a distinctive class of compounds whose aqueous solutions exhibit the following properties:. Acidic solutions have a pH less than 7, with lower pH values corresponding to increasing acidity. Common examples of acids include acetic acid in vinegar , sulfuric acid used in car batteries , and tartaric acid used in baking. The strength of an acid refers to how readily an acid will lose or donate a proton, oftentimes in solution. A stronger acid more readily ionizes, or dissociates, in a solution than a weaker acid.
The acid-base reaction class has been studied for quite some time. In , Robert Boyle reported traits of acid solutions that included their ability to dissolve many substances, to change the colors of certain natural dyes, and to lose these traits after coming in contact with alkali base solutions. In the eighteenth century, it was recognized that acids have a sour taste, react with limestone to liberate a gaseous substance now known to be CO 2 , and interact with alkalis to form neutral substances. In , Humphry Davy contributed greatly to the development of the modern acid-base concept by demonstrating that hydrogen is the essential constituent of acids. Around that same time, Joseph Louis Gay-Lussac concluded that acids are substances that can neutralize bases and that these two classes of substances can be defined only in terms of each other. The significance of hydrogen was reemphasized in when Svante Arrhenius defined an acid as a compound that dissolves in water to yield hydrogen cations now recognized to be hydronium ions and a base as a compound that dissolves in water to yield hydroxide anions.
The Arrhenius theory is simple and useful. It explains many properties and reactions of acids and bases. For instance, mixing hydrochloric acid (HCl) with sodium.
Overview of Acids and Bases
Swedish Svante Arrhenius, in proposed the concept of acid and base based on the theory of ionization. This concept is only applicable to those compounds which dissolved in aqueous solution or you can say where water is the solvent. It covers many common acids, bases and their chemical reactions, but there are also other compounds that have the characteristics of acids and bases but they do not fit into Arrhenius concept.
This definition is not wrong; it is simply limited.