Let's classify each substance as a strong acid, strong base, weak acid, or weak base:
### Strong Acids
1. HCl - Hydrochloric acid is a strong acid.
2. H₂SO₄ - Sulfuric acid is a strong acid.
3. HNO₃ - Nitric acid is a strong acid.
4. HI - Hydriodic acid is a strong acid.
### Weak Acids
1. CH₃COOH - Acetic acid is a weak acid.
2. H₂SO₃ - Sulfurous acid is a weak acid.
3. C₆H₅COOH - Benzoic acid is a weak acid.
### Strong Bases
1. KOH - Potassium hydroxide is a strong base.
2. Ca(OH)₂ - Calcium hydroxide is a strong base.
3. Ba(OH)₂ - Barium hydroxide is a strong base.
### Weak Bases
1. C₂H₅NH₂ - Ethylamine is a weak base.
2. (C₂H₅)₂NH - Diethylamine is a weak base.
By placing each substance into the appropriate category, we get:
- Strong Acids: HCl, H₂SO₄, HNO₃, HI
- Weak Acids: CH₃COOH, H₂SO₃, C₆H₅COOH
- Strong Bases: KOH, Ca(OH)₂, Ba(OH)₂
- Weak Bases: C₂H₅NH₂, (C₂H₅)₂NH