This series of lessons, which is partially complete, introduces the standard concepts of acids and based in water from a fairly rigorous Bronsted point of view. The development is comprehensive, and focuses on reactions and equilibria.
Initially Bronsted reactions, acids, bases, conjugates, dissociation constants, pH, pK's etc. are defined. The conjugate strength relationship is developed both quantitatively and qualitatively. Strong acid and bases (stronger than H3O+ or OH-, respectively) have conjugates that are very weak (weaker than water), and vice versa. The conjugate strength relationship is vital: students discover that there's nothing mysterious about "hydrolysis" when they recognise NH4+ as just another weak acid and OAc- as just another weak base. In addition, it is no surprise that OCH3- and H- are strong bases.
An entire lesson is devoted to determining equilibrium constants of reactions, and in particular finding big-K (quantitative) reactions and very-small-K reactions (which effectively don't go at all). Another lesson uses this information to show how to get as close as possible to equilibrium without doing any K calculations, simply by finding all the big-K reactions and running them to completion.
Only then does the student learn how to do the classic pH calculations for strong and weak acids and bases. The lesson in which this is done starts out requiring the student to analyze each solution to decide which solutes (possibly including water) control the pH.
With the tools all in place, the analysis and design on buffers, the analysis of titration curves, and the design of titrations (especially indicator choice for mono- and difunctional analytes) is quite straightforward.
# 1. Bronsted Acids and Bases, defines Bronsted acids and bases and their conjugates. It introduces strength, and uses Ka and Kb in a qualitative sense. The emphasis is on recognising the properties of solutions of strong, weak and very weak acids and bases.
#2. Acids and Bases in Water, proceeds to pH, the relationship between [H3O+] and [OH-], and the KaKb relationship between conjugates.
#3, Neutralization Reactions, is concerned with finding reactions, such as that between OAc- and H3O+, which proceed essentially to completion, and their inverses, which hardly go at all.
#4, Neutralization Equilibrium, uses the ideas of the previous lesson, and the reaction table, to get as close as possible to the equilibrium state by running any quantitative reactions to completion.
#5, A Single Acid or Base in Water, presents the usual pH calculations. The preparation in the previous lessons ensures that species such as NH4+ and CH3O- will be recognised and dealt with simply as further examples of known situations.
#6, Buffer Solutions, shows how buffers behave, and gives practice in designing them.
#7, Acid-Base Titrimetry, introduces the techniques of titration, and provides practice in titration of strong acids and bases.
#8, Titration Curves, shows how pH varies as a weak acid or base is titrated.
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Updated July 6, 2001