📘Class 10 Science – Chapter: Acids, Bases, and Salts Notes
✨ Introduction to Acids, Bases, and Salts
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Substances can be categorized as acids, bases, or salts based on their chemical properties.
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They are commonly found in food, medicine, cleaning products, etc.
Examples:
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Acids: Lemon juice (Citric acid), Vinegar (Acetic acid)
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Bases: Baking soda (Sodium bicarbonate), Soap (Sodium salt of fatty acid)
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Salts: Common salt (NaCl), Washing soda (Na₂CO₃)
🔹 Acids
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Acids are substances that release H⁺ ions in aqueous solutions.
| Property | Description |
|---|---|
| Taste | Sour |
| pH value | Less than 7 |
| Litmus Test | Blue litmus turns red |
| Examples | HCl, H₂SO₄, HNO₃ |
Chemical Equation:
HCl → H⁺ + Cl⁻
Examples:
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Hydrochloric acid (HCl)
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Sulphuric acid (H₂SO₄)
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Nitric acid (HNO₃)
🔹 Bases
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Bases are substances that release OH⁻ ions in aqueous solutions.
| Property | Description |
|---|---|
| Taste | Bitter |
| pH value | More than 7 |
| Litmus Test | Red litmus turns blue |
| Examples | NaOH, KOH, Ca(OH)₂ |
Chemical Equation:
NaOH → Na⁺ + OH⁻
Examples:
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Sodium hydroxide (NaOH)
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Potassium hydroxide (KOH)
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Calcium hydroxide (Ca(OH)₂)
🔹 Indicators
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Indicators help identify whether a substance is acidic or basic.
| Indicator | In Acidic Solution | In Basic Solution |
|---|---|---|
| Litmus | Blue → Red | Red → Blue |
| Methyl Orange | Orange → Red | Orange → Yellow |
| Phenolphthalein | Colourless | Pink |
🔹 Neutralization Reaction
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When acid reacts with base to form salt and water.
General Equation:
Acid + Base → Salt + Water
Example:
HCl + NaOH → NaCl + H₂O
🔹 Strength of Acids and Bases
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Measured by pH scale (0 to 14)
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pH < 7: Acidic
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pH = 7: Neutral
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pH > 7: Basic
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Example:
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Gastric juice pH = 1.2 (Highly acidic)
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Soap solution pH = 9 (Mildly basic)
🔹 Important Acids and Bases in Daily Life
| Substance | Nature | Use |
|---|---|---|
| HCl (Stomach acid) | Acid | Helps in digestion |
| NaOH (Caustic soda) | Base | Used in soap making |
| H₂SO₄ (Sulphuric acid) | Acid | Used in car batteries |
| Ca(OH)₂ (Slaked lime) | Base | Used in whitewashing |
🔹 Salts
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Formed by neutralization of acid and base.
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Can be acidic, basic, or neutral.
Examples:
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NaCl: Neutral salt
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CH₃COONa: Basic salt
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NH₄Cl: Acidic salt
Equation:
HCl + NaOH → NaCl + H₂O
🔹 Important Salts and Their Uses
| Salt Name | Formula | Use |
|---|---|---|
| Sodium chloride | NaCl | Table salt |
| Baking soda | NaHCO₃ | Used in baking, antacids |
| Washing soda | Na₂CO₃ | Used in cleaning, softening water |
| Bleaching powder | CaOCl₂ | Disinfectant, bleaching agent |
🔹 Water of Crystallization
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Water molecules present in crystalline form of a salt.
Example:
CuSO₄.5H₂O (Blue vitriol)
On heating:
CuSO₄.5H₂O → CuSO₄ (White) + 5H₂O