Acids and bases touch upon virtually all areas of chemistry, biochemistry, and physiology. This set of lessons will get you started by presenting the underlying concepts in a systematic way. Aside from the section on pH which presumes an elementary knowledge of logarithms. The subject of acid-base equilibrium calculations is not covered in this lesson. 10.1: Introduction to Acids and Bases The concepts of an acid, a base, and a salt are very old ones that have undergone several major refinements as chemical science has evolved. Our treatment of the subject at this stage will be mainly conceptual and qualitative, emphasizing the definitions and fundamental ideas associated with acids and bases. We will not cover calculations involving acid-base equilibria in these lessons. 10.2: Aqueous Solutions- pH and Titrations As you will see in the lesson that follows this one, water plays an essential role in acid-base chemistry as we ordinarily know it. To even those who know very little about chemistry, the term pH is recognized as a measure of "acidity", so the major portion of this unit is devoted to the definition of pH and of the pH scale. But since these topics are intimately dependant on the properties of water and its ability do dissociate into hydrogen and hydroxyl ions. 10.3: Acid-base reactions à la Brønsted In this lesson we develop this concept and illustrate its applications to "strong" and "weak" acids and bases, emphasizing the common theme that acid-base chemistry is always a competition between two bases for the proton. In the final section, we show how the concept of "proton energy" can help us understand and predict the direction and extent of common types of acid-base reactions without the need for calculations. 10.4: Acid-Base Reactions Will this acid react with that base? And if so, to what extent? These questions can be answered quantitatively by carrying out the detailed equilibrium calculations you will learn about in another lesson. However, modern acid-base chemistry offers a few simple principles that can enable you to make a qualitative decision at a glance. More importantly, the ideas which we develop in this section are guaranteed to give you a far better conceptual understanding of proton-based acid-base reactions. 10.5: Lewis Acids and Bases The Brønsted-Lowry proton donor-acceptor concept has been one of the most successful theories of Chemistry. But as with any such theory, it is fair to ask if this is not just a special case of a more general theory that could encompass an even broader range of chemical science. In 1916, G.N. Lewis of the University of California proposed that the electron pair is the dominant actor in acid-base chemistry. 10.6: Types of Acids and Bases You will already have noticed that not every compound that contains hydrogen atoms is acidic; .e.g, ammonia gives an alkaline aqueous solution. Similarly, some compounds containing the group -OH are basic, but others are acidic. An important part of understanding chemistry is being able to recognize what substances will exhibit acidic and basic properties in aqueous solution. Fortunately, most of the common acids and bases fall into a small number of fairly well-defined groups. 10.7: Acid-Base Gallery Acids and bases are of interest not only to the chemically inclined; they play a major role in our modern industrial society — so anyone who participates in it, or who is interested in its history and development, needs to know something about them. Five of the major acids and bases fall into the "Top 20" industrial chemicals manufactured in the world.