ICSE Class 10 Chemistry: Acids, Bases and Salts — Important Questions with Answers 2026

Short Answer Questions (2-3 Marks)

• Q: Define acid and base according to Arrhenius theory.
  Ans: According to Arrhenius: An acid is a substance that produces H⁺ (H₃O⁺) ions in aqueous solution. Example: HCl → H⁺ + Cl⁻. A base is a substance that produces OH⁻ ions in aqueous solution. Example: NaOH → Na⁺ + OH⁻. Neutralisation: H⁺ + OH⁻ → H₂O.
• Q: What is pH? What is the pH range of acids and bases?
  Ans: pH is the negative logarithm of hydrogen ion concentration. pH = -log[H⁺]. pH scale ranges from 0 to 14. pH < 7: acidic (lower pH = stronger acid). pH = 7: neutral. pH > 7: basic/alkaline (higher pH = stronger base). pH of blood: 7.4, pH of lemon juice: ~2.
• Q: What happens when an acid reacts with (i) a metal, (ii) a metal carbonate, (iii) a base?
  Ans: (i) Acid + Metal → Salt + Hydrogen gas. Example: 2HCl + Zn → ZnCl₂ + H₂↑. (ii) Acid + Metal carbonate → Salt + Water + CO₂. Example: 2HCl + CaCO₃ → CaCl₂ + H₂O + CO₂↑. (iii) Acid + Base → Salt + Water (Neutralisation). Example: HCl + NaOH → NaCl + H₂O.
• Q: Define: (i) Normal salt, (ii) Acid salt, (iii) Basic salt. Give one example each.
  Ans: (i) Normal salt: Formed by complete neutralisation. No replaceable H⁺ or OH⁻. Example: NaCl. (ii) Acid salt: Formed by incomplete neutralisation of a polybasic acid. Contains replaceable H⁺. Example: NaHSO₄. (iii) Basic salt: Formed by incomplete neutralisation of a polyacidic base. Contains replaceable OH⁻. Example: Mg(OH)Cl.
• Q: What is a neutralisation reaction? Give the equation for neutralisation of HCl with NaOH.
  Ans: A neutralisation reaction is a chemical reaction between an acid and a base to form salt and water. HCl + NaOH → NaCl + H₂O. The ionic equation: H⁺(aq) + OH⁻(aq) → H₂O(l). Neutralisation is an exothermic reaction (heat is released).

Long Answer / Application Questions (4-6 Marks)

• Q: How is washing soda prepared from baking soda? Give equations.
  Ans: Step 1: Baking soda is heated — 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂↑ (soda ash formed). Step 2: Soda ash is recrystallised — Na₂CO₃ + 10H₂O → Na₂CO₃.10H₂O (washing soda). Uses of washing soda: water softening, glass manufacture, laundry.

Exam Tips for This Chapter

• Revise all definitions and laws from Acids, Bases and Salts — they are commonly asked as 1-2 mark questions
• Practice diagrams related to Acids, Bases and Salts — neat labelled diagrams carry 2-3 marks
• For numericals, always show formula → substitution → answer with correct units
• Previous year analysis shows Acids, Bases and Salts carries 8-12 marks in the board exam