What Are Acids and Bases?
- Acids donate H⁺ ions (protons) in solution (pH < 7)
- Bases accept H⁺ ions or donate OH⁻ ions (pH > 7)
- Neutral substances have a pH of 7 (e.g., pure water)
- The pH scale measures acidity/basicity from 0 (most acidic) to 14 (most basic)
- Indicators like litmus paper change color to show pH
The pH Scale
The pH scale ranges from 0 to 14:
- 0-3: Strong acids (battery acid, stomach acid)
- 4-6: Weak acids (coffee, orange juice)
- 7: Neutral (pure water)
- 8-10: Weak bases (seawater, baking soda)
- 11-14: Strong bases (bleach, drain cleaner)
Strong vs. Weak Acids/Bases
Acids
- Strong Acids: Fully dissociate in solution (e.g., HCl, H₂SO₄, HNO₃)
- Weak Acids: Partially dissociate (e.g., acetic acid, citric acid)
Bases
- Strong Bases: Fully ionize (e.g., NaOH, KOH, Ca(OH)₂)
- Weak Bases: Partially ionize (e.g., NH₃, CH₃NH₂)
Note: Strength is different from concentration. A weak acid can be concentrated, and a strong acid can be dilute.
Acid-Base Reactions
Neutralization
The general neutralization reaction is:
Acid + Base → Salt + Water
Example:
HCl + NaOH → NaCl + H₂O
Everyday Examples
- Antacids neutralizing stomach acid
- Vinegar (acid) reacting with baking soda (base)
- Bee stings (acidic) treated with baking soda
- Wasp stings (basic) treated with vinegar