Understanding pH and pOH
pH is a scale used to specify the acidity or basicity of an aqueous solution. It ranges roughly from 0 to 14. Acidic solutions have a pH less than 7, while basic (alkaline) solutions have a pH greater than 7. A pH of 7 is neutral (pure water at 25°C).
Key Formulas
The relationship between pH, pOH, and ion concentration is governed by these equations:
- pH = -log[H+] (Negative log of Hydrogen ion concentration)
- pOH = -log[OH-] (Negative log of Hydroxide ion concentration)
- pH + pOH = 14 (At 25°C)
The pH Scale Reference
| pH Range | Substance Example | Classification |
|---|---|---|
| 0 - 3 | Battery Acid, Stomach Acid | Strong Acid |
| 4 - 6.9 | Orange Juice, Coffee | Weak Acid |
| 7.0 | Pure Water | Neutral |
| 7.1 - 10 | Sea Water, Baking Soda | Weak Base |
| 11 - 14 | Bleach, Ammonia | Strong Base |