1. Hydrogen Ions and Acidity
Chapter 19.2

2. What is Kw?
Kw is the equilibrium constant for the self-ionization of water
Water molecules are in constant motion and can collide to create a hydronium ion and a hydroxide ion

3. Where does Kw come from?
2H2O(l)  H3O+(aq) + OH-(aq)
Kw = [H+][OH-]
__________
[H2O]2
But we remove liquids and solids
Kw = [H+][OH-]

4. Self Ionization Concentration Ion-Product Constant
Called the self-ionization of water
[H+] = [OH-] = 1.0 x 10-7 M
The ion-product constant for water (Kw)
Kw = [H+][OH-] = 1.0 x M2
Neutral solution [H+]=[OH-]
Acidic solution [H+] > [OH-]
Basic solution [H+] < [OH-]

5. pH Scale and Formulas
pH is an easier way to express the strengths of acids and bases
pH scale ranges from 0-14
0-6 considered acidic RED
7 considered neutral
8-14 considered basic BLUE
pH = -log [H+] [H+] = antilog(pH)
pOH = -log [OH-] [OH-] = antilog(pOH)
pH + pOH = [H+][OH-] = 1.0 x 10-14

6. Practice Problems
What is the pH of a substance that has an [H+] concentration of 1 x 10-4? What about 1 x 10-5?
What is the pH of a substance that has an [H+] concentration of x 10-5?
4.0; 5.0; 4.2

7. Practice Problems
What is the [H+] concentration of a substance that has a pH of 8.00? What is the [OH-] concentration?
What is the [H+] concentration of a substance that has a pH of 8.73? What is the [OH-] concentration? What is the pOH?
1 x 10-8;1 x 10-6;1.86 x 10-9;5.39 x 10-6; 5.27