Acids
Acids are substances that produce H⁺ ions (hydrogen ions) in water.
Properties of Acids
- Sour taste (e.g., lemon juice, vinegar)
- Turn blue litmus red
- pH less than 7
- React with metals to produce hydrogen gas
- React with carbonates to produce CO₂
Examples
| Acid | Formula | Found in |
|---|---|---|
| Hydrochloric acid | HCl | Stomach |
| Sulphuric acid | H₂SO₄ | Batteries |
| Nitric acid | HNO₃ | Fertilizers |
| Acetic acid | CH₃COOH | Vinegar |
| Citric acid | C₆H₈O₇ | Citrus fruits |
Bases
Bases are substances that produce OH⁻ ions in water. Bases that are soluble in water are called alkalis.
Properties of Bases
- Bitter taste, soapy feel
- Turn red litmus blue
- pH greater than 7
Salts
Salts are formed when an acid reacts with a base (neutralisation).
Acid + Base → Salt + Water
HCl + NaOH → NaCl + H₂O
Important Salts
| Salt | Chemical Name | Use |
|---|---|---|
| NaCl | Sodium chloride | Table salt, preservative |
| NaHCO₃ | Sodium hydrogen carbonate | Baking soda, antacid |
| Na₂CO₃ | Sodium carbonate | Washing soda, glass making |
| CaOCl₂ | Bleaching powder | Disinfectant |
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Frequently Asked Questions
The pH scale measures the acidity or basicity of a solution, ranging from 0 to 14. pH less than 7 is acidic, pH 7 is neutral, and pH greater than 7 is basic (alkaline).