L3 - Equilibrium Law and the Strength of Acids and Bases
Introduction
The pH of solutions provides important information about the equilibrium of acidic and basic solutes. In the previous lessons you used solution pH and molar concentration of the solute to calculate a percent ionization. In previous module you learned about equilibrium law and Kc, the equilibrium constant. Can Kc be calculated for acidic and basic solutions? What would a difference in the value for the equilibrium constant for two acids or bases tell you about their equilibrium?
You may recall reading in the textbook that the pH of rainwater is normally 5.5. The presence of dissolved carbon dioxide from the atmosphere in the rain droplets results in the formation of carbonic acid, which in turn ionizes to produce hydronium ions. Why is the pH of rainwater expected to be 5.5?
In this lesson you will investigate the use of quantitative techniques to describe the equilibrium of aqueous acids and bases. You will also investigate how the equilibrium influences the pH of both strong and weak acids and bases.
Consider the following questions as you complete this lesson:
- What are Ka, Kb, and Kw?
- How do Ka and Kb explain the position of the equilibrium of aqueous acids and bases?
- How are values for Ka and Kb used to calculate the pH of solutions containing weak acids and bases?