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Practical Work

ICSE Class 9 · Chemistry · Chapter 9

What this chapter covers

Past board exam questions

ICSE 2019 sample paper · 1 mark

The gas which has a rotten egg smell is:

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

ICSE 2019 sample paper · 5 marks

Name the gas evolved in each of the following cases: (i) Copper carbonate is heated strongly. (ii) Action of dilute hydrochloric acid on sodium sulphite. (iii) Nitrogen combines with hydrogen. (iv) Action of dilute sulphuric acid on sodium carbonate. (v) Addition of sodium to cold water.

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(i) Carbon dioxide (CO₂) (ii) Sulphur dioxide (SO₂) (iii) Ammonia (NH₃) (iv) Carbon dioxide (CO₂) (v) Hydrogen (H₂)

ICSE 2019 sample paper · 5 marks

What do you observe when: (i) Iodine crystals are heated in a test tube? (ii) Iron nails are added to copper sulphate solution? (iii) Lead nitrate crystals are heated strongly? (iv) Ferric chloride crystals are exposed to atmosphere for some time? (v) Blue copper sulphate crystals are heated?

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(i) The crystals sublime: violet vapours are seen, which condense back to shiny grey-black crystals on the cooler upper part of the test tube. (ii) A reddish-brown coating of copper forms on the iron nails and the blue solution gradually turns pale green (iron(II) sulphate). (iii) The crystals crackle (decrepitate), reddish-brown fumes of nitrogen dioxide and a colourless gas (oxygen) are given off, and a residue is left that is reddish-brown when hot and yellow when cold (lead monoxide). (iv) The crystals are deliquescent: they absorb moisture from the air and dissolve in it, forming a yellowish-brown solution. (v) The crystals lose their water of crystallisation and turn into a white …

ICSE 2019 sample paper · 4 marks

How would you distinguish between the following pairs of substances on the basis of the chemical tests given in brackets? (i) Sodium Chloride and Potassium Chloride (flame test) (ii) Zinc Carbonate and Lead Carbonate (dry heating)

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(i) Flame test: sodium chloride imparts a golden-yellow colour to the non-luminous flame, while potassium chloride imparts a lilac (pale violet) colour. (ii) On dry heating both give carbon dioxide (turns lime water milky). Zinc carbonate leaves a residue of zinc oxide that is yellow when hot and white when cold: ZnCO₃ → ZnO + CO₂. Lead carbonate leaves a residue of lead monoxide that is reddish-brown when hot and yellow when cold: PbCO₃ → PbO + CO₂.