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ICSE Class 10 · Chemistry · Chapter 13

What this chapter covers

Past board exam questions

ICSE 2027 sample paper · 1 mark

When compound X reacts with dilute hydrochloric acid, it releases a gas that turns moist lead acetate paper black and decolourises acidified potassium permanganate solution. Which of the following is compound X?

  1. Sodium nitrate
  2. Sodium sulphide
  3. Sodium carbonate
  4. Sodium sulphite
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Sodium sulphide

ICSE 2026 sample paper · 1 mark

When compound X reacts with dilute sulphuric acid, it releases a gas that turns acidified potassium dichromate solution from orange to green. Which of the following could be compound X?

  1. Lead nitrate
  2. Copper carbonate
  3. Sodium chloride
  4. Potassium sulphite
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Potassium sulphite

ICSE 2026 board paper · 2 marks

Alex was given a solution of an unknown salt Y for analysis. He performed the following tests and recorded his observations: • To a part of the solution Y, he added silver nitrate solution and obtained a white precipitate which was soluble in ammonium hydroxide solution. • To the remaining solution he added a few drops of sodium hydroxide solution and obtained a pale blue precipitate. Based on the observations made by Alex, identify: (a) the anion and (b) the cation present in salt Y.

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(a) Chloride ion (Cl⁻) — white precipitate of AgCl, soluble in NH₄OH. (b) Copper (II) ion (Cu²⁺) — pale blue precipitate of Cu(OH)₂. (Salt Y is copper (II) chloride, CuCl₂.)

ICSE 2025 board paper · 1 mark

Which gas decolourises potassium permanganate (KMnO₄) solution?

  1. Sulphur dioxide
  2. Ammonia
  3. Hydrogen chloride
  4. Carbon dioxide
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Sulphur dioxide

ICSE 2025 board paper · 3 marks

Give one significant observation when: (a) a solution of barium chloride is added to zinc sulphate solution. (b) lead nitrate is heated in a test tube. (c) chlorine gas is passed over moist starch iodide paper.

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(a) A white precipitate of barium sulphate is formed (insoluble in dilute acids). (b) The crystals crackle (decrepitate), reddish-brown nitrogen dioxide gas is evolved and a yellow residue of lead monoxide is left: 2Pb(NO₃)₂ → 2PbO + 4NO₂ + O₂. (c) The moist starch iodide paper turns blue-black (chlorine liberates iodine, which gives a blue-black colour with starch).

ICSE 2025 compartment paper · 3 marks

Harsh performed the following experiments in the laboratory. State one significant observation made by Harsh when: (a) he added concentrated sulphuric acid to blue vitriol. (b) he passed ammonia gas over heated PbO. (c) sodium hydroxide solution was added to CuSO₄ solution by him.

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(a) The blue crystals of CuSO₄·5H₂O turn white (anhydrous CuSO₄), because conc. H₂SO₄ removes the water of crystallisation. (b) The buff yellow PbO turns into a grey (silvery) metallic residue of lead, and droplets of water appear: 3PbO + 2NH₃ → 3Pb + 3H₂O + N₂. (c) A pale blue precipitate of copper hydroxide forms, which is insoluble in excess NaOH: CuSO₄ + 2NaOH → Cu(OH)₂↓ + Na₂SO₄.

ICSE 2025 compartment paper · 3 marks

Choose the letters L, M, N, O & P to match the description (a) to (c) given below: [L – Ammonia, M – Nitrogen, N – Hydrogen sulphide, O – Hydrogenchloride gas, P – Nitrogen dioxide] (a) When this gas comes in contact with ammonia dense white fumes are seen. (b) The gas that turns moist lead acetate paper silvery black. (c) The gas produced on heating lead nitrate.

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(a) O – Hydrogen chloride gas (NH₃ + HCl → NH₄Cl, dense white fumes) (b) N – Hydrogen sulphide (forms black PbS) (c) P – Nitrogen dioxide (2Pb(NO₃)₂ → 2PbO + 4NO₂ + O₂)

ICSE 2025 board paper · 3 marks

You are provided with some compounds in the box. PbO, CH₄, PbO₂, CO₂, HCl, NCl₃, SO₂ Choose the most appropriate compound which fits the descriptions (a) to (c) given below: (a) A colourless gas which turns acidified K₂Cr₂O₇ from orange to green. (b) A yellow explosive oily liquid formed when excess chlorine gas reacts with ammonia gas. (c) A yellow metallic oxide formed on thermal decomposition of PbCO₃.

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(a) SO₂ (b) NCl₃ (NH₃ + 3Cl₂ → NCl₃ + 3HCl) (c) PbO (PbCO₃ → PbO + CO₂)