Module 5 Intro

Module 5—Acids and Bases

Lesson Summary

In this lesson you explored the following essential questions:

• What are the empirical properties of acids and bases?
  
  
• How are acids and bases named?
  
  
• Why is Arrhenius's original theory considered to be an incomplete explanation of the behaviour of acids and bases?

Empirical properties can be used to distinguish acids and bases from neutral substances. Taste, feel, pH, reactivity, and conductivity are all useful diagnostic tests for this purpose.

While acids and bases can be used in applications without a theoretical understanding of their behaviour, chemists require a systematic way of dealing with this large class of substances. Naming rules have been developed to allow for effective communication regarding acids and bases. It is very important that you learn how to name acids and bases—you will encounter them frequently.

Since Arrhenius's original theory does not successfully predict all experimental results, scientists were forced to revise, restrict, or replace the theory. The revised (modified) Arrhenius theory can successfully explain many empirical properties of acids and bases, but it is unable to actually predict whether a particular reaction will take place.

For example, the modified Arrhenius theory cannot predict whether H2PO4–(aq) is an acid or a base. Despite the problems associated with the modified Arrhenius theory, it is still a dramatic improvement over Arrhenius’s original theory.

Lesson Glossary

hydronium ion: a hydrated hydrogen ion (proton), H3O+(aq); the entity responsible for the acidic properties in an aqueous solution