Notes of Ch 2. Acids, Bases and Salts, Class 10th Science

Chapter 2: Acids, Bases and Salts

Chapter 2: Acids, Bases and Salts

Acids

The term ‘acid’ is derived from the Latin word acidus, meaning sour.

Acids are chemical substances that have a sour taste and turn blue litmus solution red. According to Arrhenius, acids are substances that furnish H+ ions in aqueous solutions.

Example:

H2SO4 → 2H+ + SO42-

Properties of Acids

Physical Properties:
  • Sour in taste
  • Change blue litmus to red
  • Conduct electricity in solution
  • Produce H+ ions in water
Chemical Properties:
  • React with metals to liberate hydrogen gas
  • React with carbonates/hydrogen carbonates to release CO2
  • React with metal oxides to form salt and water

Natural Sources of Acids

Substance Organic Acid
Orange, Lemon Citric Acid, Ascorbic Acid (Vitamin C)
Apple Malic Acid
Vinegar Acetic Acid
Curd (Sour Milk) Lactic Acid
Tomato Oxalic Acid
Red Ants Formic Acid

Types of Acids

1. Mineral Acids: Acids obtained from rocks and minerals.
2. Organic Acids: Acids found in plants and animals.
Name Type of Acid Chemical Formula Uses
Hydrochloric Acid Mineral Acid HCl Purification of NaCl, making Aqua Regia
Sulphuric Acid Mineral Acid H2SO4 Used in car batteries and refining petroleum
Lactic Acid Organic Acid CH3CH(OH)COOH Food preservative, flavoring agent
Citric Acid Organic Acid C6H8O7 Preserving agent, used in soft drinks

Bases

Bases are substances that turn red litmus blue and produce OH⁻ ions in water. Some bases are soluble in water, these are called alkalis.

Properties of Bases

Physical Properties:
  • Bitter taste
  • Slippery to touch
  • Turn red litmus to blue
Chemical Properties:
  • React with acids to form salt and water (Neutralization reaction)
  • React with metals to liberate hydrogen gas

Reactions of Acids and Bases

Acids with Metals:

Acid + Metal → Salt + Hydrogen Gas

Example: 2HCl + Zn → ZnCl2 + H2

Bases with Metals:

Base + Metal → Salt + Hydrogen Gas

Example: 2NaOH + Zn → Na2ZnO2 + H2

Neutralization Reaction:

Acid + Base → Salt + Water

Example: HCl + NaOH → NaCl + H2O

Indicators

Indicators are substances that change color in acids and bases.

Types of Indicators:

  • Natural Indicators: Litmus, Red cabbage extract, Turmeric
  • Synthetic Indicators: Methyl orange, Phenolphthalein
  • Olfactory Indicators: Substances that change odor in acidic and basic solutions