1. pH Scale Strengths of Acids and Bases
Chapter 23.2
pH Scale
Strengths of Acids and Bases

2. Strong and Weak Acids
Strong acid: nearly all the acid molecules dissociate into ions
Example: HCl, Sulfuric Acid
Weak acid: only a small fraction of molecules dissolve in water
Example: vinegar

3. Strong and Weak Bases
Strong base: Dissociates completely in a solution.
Example: Sodium hydroxide
Weak base: does not dissociate completely in a solution
Example: ammonia

4. Indicators
Indicator: Organic substance that changes color in an acid or base
Examples:
litmus - red/blue
phenolphthalein - colorless/pink
red cabbage juice - pink/green

5. pH of a Solution
The pH of a solution is a measure of the concentration of H+ ions in it.
The pH measures how acidic or basic a solution is.
The greater the H+ concentration is, the lower the pH is and the more acidic the solution is.

6. pH Scale pH Scale ranges from 0 to 14 Less than 7 = Acid
Equal to 7 = neutral
Greater than 7 = Base 7
INCREASING
ACIDITY
NEUTRAL
BASICITY 14

7. How to remember what’s what
Acid comes before Base in the alphabet
Low numbers come before high numbers
Acids = low numbers
Bases = high numbers

8. pH of Common Substances
pH Scale
pH of Common Substances