ACIDS AND

Reactions of Acids and Bases

1. Reaction of Acids and Metal Carbonates

• Metal Carbonates: Compounds containing a metal, carbon, and oxygen. React with dilute acids.
• When an acid reacts with a metal carbonate:
  • Products: Salt, water, and carbon dioxide.
  • General Word Equation:
    \text{acid} + \text{metal carbonate} \rightarrow \text{salt} + \text{water} + \text{carbon dioxide}
  • Example: Reaction of nitric acid and calcium carbonate produces calcium nitrate, water, and carbon dioxide:
    \text{nitric acid} + \text{calcium carbonate} \rightarrow \text{calcium nitrate} + \text{water} + \text{carbon dioxide}
• Observation: Bubbles of gas produced during the reaction.
• Testing for Carbon Dioxide: Bubbling gas through limewater turns it cloudy, indicating the presence of carbon dioxide.

2. Neutralisation Reactions

• Neutralisation is the reaction between an acid and an alkali.
• Effect of Adding Alkalis:
  • Adding alkalis neutralises acids, raising the pH towards 7 (neutral).
• Titration: A technique used to measure the volumes of acids and alkalis accurately for neutralisation.
• Real-Life Applications:
  • Indigestion treatment with antacids (e.g., magnesium hydroxide).
  • Adding lime to acidic soils aids plant growth.
  • Baking soda neutralises bee stings; vinegar neutralises wasp stings.

3. Properties of Acids and Alkalis

• Indicators: Substances that change color in acid/alkali solutions.
• pH Scale:
  • Range: 0 (acidic) to 14 (alkaline); 7 is neutral.
  • Universal indicator shows color changes at varying pH levels.
• Common Acids and Alkalis:
  • Acids: Hydrochloric acid, sulfuric acid, nitric acid.
  • Alkalis: Sodium hydroxide, potassium hydroxide, ammonia.

4. Neutralisation Reactions and Salts

• The general equations for neutralisations:
  • With Metal Oxides:
    \text{acid} + \text{metal oxide} \rightarrow \text{salt} + \text{water}
  • With Metal Carbonates:
    \text{acid} + \text{metal carbonate} \rightarrow \text{salt} + \text{water} + \text{carbon dioxide}
  • With Metals:
    \text{acid} + \text{metal} \rightarrow \text{salt} + \text{hydrogen}
• Examples of salts produced:
  • Hydrochloric acid + sodium hydroxide yields sodium chloride + water.

5. Acid Rain

• Acid rain is caused by sulfur dioxide and nitrogen oxides dissolving in rainwater, forming sulfuric and nitric acids. Effects include:
  • Damage to soils, plant life, and aquatic ecosystems.
  • Erosion of buildings made of limestone.
• Mitigation strategies:
  • Burning less fossil fuels.
  • Removing sulfur from fossil fuels before combustion.