Module 5 Intro

1. Module 5 Intro

1.29. Page 7

Lesson 4

Module 5—Acids and Bases

Lesson Summary

The following critical questions were discussed in this lesson:

How are ionization and dissociation accounted for when calculating the concentration of acidic and basic particles within a solution?
How can a solution’s pH be predicted using information including mass of solute and solution volume?
Why is the pH of a diluted solution able to be predicted?

By using the algorithms and techniques learned in Modules 4 and 5, it is possible to prepare acidic and basic solutions to desired concentrations and pH.

Formula	Formula may be used when …	Formula may not be used when …
pH = − log [H3O+]	the concentration of a strong acid is given. the hydronium-ion concentration is explicitly stated in the question, even if it is for a weak or polyprotic acid.	the concentration of a polyprotic acid or a weak acid is given.
[H3O+] = 10–pH	the pH of any solution is given.
pH = − log [OH–]	the concentration of a strong base is given. the hydroxide-ion concentration is explicitly stated in the question, even if it is for a weak or polyprotic base.	the concentration of a polyprotic acid or a weak base is given.
[OH–] = 10–pOH	the pOH of any solution is given.

In situations where concentrated stock solutions of acids and bases are available, dilution of a sample of the stock solution is an alternative. When a stock solution is not available, appropriate quantities of solutes (as solids or gases) must be dissolved. When preparing acidic and basic solutions, you should be very aware of safety concerns and use appropriate techniques for handling these substances.