CBSE Class 10 Science: Acids, Bases & Salts — Notes 2026

Acids — Properties and Examples

• Sour taste; turn blue litmus red; pH < 7; dissolve in water to give H⁺
• Mineral acids: HCl, H₂SO₄, HNO₃; organic acids: acetic, citric, tartaric, lactic, formic, oxalic
• Concentrated vs. dilute acids; diluting H₂SO₄ — always add acid to water (exothermic)

Bases and Alkalis

• Bitter taste, slippery feel; turn red litmus blue; pH > 7; give OH⁻ in water
• Alkali: soluble base (NaOH, KOH, Ca(OH)₂); all alkalis are bases but not vice versa
• Baking soda: NaHCO₃ (amphoteric character); used in cooking and antacids

Universal Indicator and pH Scale

• Universal indicator is a mixture of indicators; shows range of colours for different pH
• pH = −log[H⁺]; pH 0–6 (acids), 7 (neutral), 8–14 (bases)
• Importance of pH: rain (5.6), blood (7.4), neutral (7.0); acid rain < 5.6

Reactions of Acids and Bases

• Acid + metal → salt + H₂; acid + metal carbonate → salt + H₂O + CO₂
• Neutralisation (acid + base → salt + water): used in antacids, toothpaste
• Soap making (saponification): fat + strong base → glycerol + soap

Salts — Preparation and Types

• Normal salts (NaCl, Na₂SO₄), acidic salts (NaHSO₄, NaHCO₃), basic salts (Mg(OH)Cl)
• Preparation of NaCl: reaction of HCl with NaOH; evaporation of brine
• Water of crystallisation: CuSO₄·5H₂O (blue vitriol), Na₂CO₃·10H₂O (washing soda), CaSO₄·2H₂O (gypsum)

Important Compounds

• Bleaching powder (CaOCl₂): made from Ca(OH)₂ + Cl₂; disinfects water
• Baking soda (NaHCO₃): antacid, fire extinguisher, baking; decomposes on heating
• Washing soda (Na₂CO₃·10H₂O): softens hard water; used in glass, soap, paper industries

CBSE Exam Questions

• State the chemical name and formula of plaster of Paris; how is it prepared from gypsum?
• Explain why bee sting causes pain and how to relieve it
• Name the acid present in ant sting and the remedy