Class 10 Science: Acids, Bases, and Salts
Acids
• Definition: Substances that release hydrogen ions (H⁺) when dissolved in water.
• Properties:
• Sour taste.
• Turn blue litmus paper red.
• React with metals to produce hydrogen gas.
• React with bases to form salt and water (neutralization).
• Conduct electricity in aqueous solutions.
• Examples: Hydrochloric acid (HCl), sulfuric acid (H₂SO₄), acetic acid (CH₃COOH).
Bases
• Definition: Substances that release hydroxide ions (OH⁻) when dissolved in water.
• Properties:
• Bitter taste.
• Soapy or slippery to touch.
• Turn red litmus paper blue.
• React with acids to form salt and water (neutralization).
• Conduct electricity in aqueous solutions.
• Examples: Sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)₂).
Salts
Salts
• Definition: Ionic compounds formed by the neutralization reaction between an acid and a base.
• Properties:
• Generally solid and crystalline at room temperature.
• Dissolve in water to form electrolyte solutions that conduct electricity.
• Can be neutral, acidic, or basic depending on the strength of the acid and base from which they are formed.
• Examples: Sodium chloride (NaCl), potassium nitrate (KNO₃), calcium sulfate (CaSO₄).
Important Concepts
• pH Scale:
• Measures the acidity or basicity of a solution.
• Scale ranges from 0 to 14; pH 7 is neutral, below 7 is acidic, above 7 is basic.
• pH = -log[H⁺]
• Indicators: Substances that change color in the presence of an acid or a base.
• Litmus: Red in acid, blue in base.
• Phenolphthalein: Colorless in acid, pink in base.
• Methyl orange: Red in acid, yellow in base.
• Neutralization Reaction: Acid + Base → Salt + Water.
• Example: HCl + NaOH → NaCl + H₂O.
• Common Uses:
• Acids: Food preservation (vinegar), industry (sulfuric acid in batteries).
• Bases: Cleaning agents (ammonium hydroxide), manufacturing (sodium hydroxide in soap making).
• Salts: Food seasoning (table salt), fertilizers (potassium nitrate).
Preparation of Salts
• From Acid and Base: By neutralization.
• Example: NaOH + HCl → NaCl + H₂O.
• From Acid and Metal: Metal reacts with acid, releasing hydrogen gas and forming salt.
• Example: Zn + H₂SO₄ → ZnSO₄ + H₂.
• From Acid and Metal Carbonate:
Carbonate reacts with acid, releasing CO₂ and forming salt and water.
• Example: CaCO₃ + HCl → CaCl₂ + CO₂ + H₂O.
• Bases: Cleaning agents (ammonium hydroxide), manufacturing (sodium hydroxide in soap making).
• Salts: Food seasoning (table salt), fertilizers (potassium nitrate).
Preparation of Salts
• From Acid and Base: By neutralization.
• Example: NaOH + HCl → NaCl + H₂O.
• From Acid and Metal: Metal reacts with acid, releasing hydrogen gas and forming salt.
• Example: Zn + H₂SO₄ → ZnSO₄ + H₂.
• From Acid and Metal Carbonate:
Carbonate reacts with acid, releasing CO₂ and forming salt and water.
• Example: CaCO₃ + HCl → CaCl₂ + CO₂ + H₂O.