Practical Work Exe-9A Chemistry Class-9 ICSE Selina Publishers

Practical Work Exe-9A Chemistry Class-9 ICSE Selina Publishers Solutions Chapter-9. Step By Step ICSE Selina Concise Solutions of Chapter-9 Practical Work with All Exercise including MCQs, Very Short Answer Type, Short Answer Type, Long Answer Type, Numerical and Structured/Application Questions Solved . Visit official Website CISCE for detail information about ICSE Board Class-9.

Practical Work Exe-9A Chemistry Class-9 ICSE Concise Selina Publishers

Board	ICSE
Publications	Selina Publication
Subject	Chemistry
Class	9th
Chapter-9	Practical Work
Book Name	Concise
Topics	Solution of Exercise – 9A (Recognition and identification of Gases)
Academic Session	2023-2024

A. Exercise – 9A

Practical Work Class-9 Chemistry Concise Solutions  

Page-150

Question 1.

(a) Give a chemical test to identify the following gases :

(i) Ammonia
(ii) Sulphur dioxide
(iii) Hydrogen chloride
(iv) Chlorine
(v) Carbon dioxide
(vi) Oxygen
(vii) Hydrogen

(b) Select a basic gas mentioned in Q.1(a). How is the basic nature verified?

(c) Select acidic gases from the gases mentioned in Q.1(a). How is the acidic nature verified?

(d) State the gas responsible for the bleaching action?

(e) Which gas turns blue cobalt chloride paper light pink?

Answer:

(a) Chemical test to identify the gases are :

(i) Ammonia — When a glass rod dipped in conc. HCl is brought near the gas, dense white fumes of ammonium chloride are formed.
(ii) Sulphur dioxide — Sulphur dioxide gas turns acidified potassium permanganate from pink to clear colourless and acidified potassium dichromate from orange to clear green.
(iii) Hydrogen chloride — Forms a curdy white ppt. on passage through AgNO3 solution. The precipitate dissolves in excess of NH4OH.
(iv) Chlorine — Pass the gas through silver nitrate solution, a white ppt. of silver chloride is formed.
(v) Carbon dioxide — When the gas is passed through lime water, it turns milky and white ppt. of calcium carbonate appears.
(vi) Oxygen — Oxygen gas rekindles a glowing wooden splinter.
(vii) Hydrogen — Hydrogen gas burns with a ‘pop’ sound in air.

(b) Ammonia is a basic gas. It turns red litmus blue.

(c) Sulphur dioxide, Hydrogen chloride, Chlorine, Carbon dioxide. It turns blue litmus red.

(d) Chlorine

(e) Water vapour

Question 2.

What is observed on performing the following :

	Hydrogen	Oxygen	Carbon dioxide	Chlorine
Litmus test
Applying burning splint to the gas
Colour of gas	colourless	colourless	colourless	greenish yellow
Odour of gas

Answer:

	Hydrogen	Oxygen	Carbon dioxide	Chlorine
Litmus test	Neutral to litmus	Neutral to litmus	blue litmus turns red	blue litmus turns red and finally bleaches
Applying burning splint to the gas	Pure hydrogen burns with a pale blue flame when a burning splinter is brought near it	rekindles a glowing splinter	burning splint is extinguished	burning splint is extinguished
Colour of gas	colourless	colourless	colourless	greenish yellow
Odour of gas	odourless	odourless	odourless	sharp pungent choking smell

 

Question 3.

Give a chemical test to distinguish between the following gases.

(a) H₂ and CO₂

(b) H₂ and O₂

(c) CO₂ and SO₂

(d) HCl and H₂S

(e) HCl and Cl₂

(f) NH₃ and HCl

(g) SO₂ and Cl₂

(h) NH₃ and SO₂

Answer:

(a) H₂ and CO₂ — Hydrogen gas is neutral to litmus whereas carbon dioxide turns blue litmus red.

(b) H₂ and O₂ — Hydrogen gas burns with a pale blue flame when a burning splinter is brought near it whereas oxygen gas rekindles a glowing wooden splinter.

(c) CO₂ and SO₂ — Carbon dioxide gas has no effect on acidified potassium permanganate (KMnO₄) and acidified potassium dichromate (K₂Cr₂O₇) solution whereas sulphur dioxide gas turns acidified potassium permanganate from pink to clear colourless and acidified potassium dichromate from orange to clear green.
2KMnO₄ + 2H₂O + 5SO₂ ⟶ K₂SO₄ + 2MnSO₄ + 2H₂SO₄
K₂Cr₂O₇ + H₂SO₄ + 3SO₂ ⟶ K₂SO₄ + Cr₂(SO₄)₃ + H₂O

(d) HCl and H₂S —

Rod dipped in ammonia solution is brought near the mouth of the two gases. HCl gives dense white fumes of ammonium chloride and hence can be distinguished from hydrogen sulphide.
NH₃(aq) + HCl ⟶ NH₄Cl

(e) HCl and Cl₂ — Chlorine (Cl₂) turns moist starch iodide paper blue black whereas HCl does not.
Cl₂ + 2KI ⟶ 2KCl + I₂
Starch + I₂ ⟶ Blue black colour

(f) NH₃ and HCl — Ammonia turns Nessler’s reagent from colourless to pale brown.
Hydrogen chloride shows no action with Nessler’s reagent. It forms a curdy white ppt. on passage through AgNO₃ solution.
AgNO₃ [ag.] + HCl ⟶ AgCl ↓ [curdy white ppt.] + HNO₃
The ppt. of AgCl is soluble in NH₄OH but insoluble in dil. HNO₃

(g) SO₂ and Cl₂ — On passing Sulphur dioxide gas through lime water, it turns lime water milky.
Ca(OH)₂ + SO₂ ⟶ CaSO₃ ↓ [white ppt.] + H₂O
Chlorine gas does not turn lime water milky. It turns moist starch iodide paper blue black.
Cl₂ + 2KI ⟶ 2KCl + I₂
Starch + I₂ ⟶ Blue black colour

(h) NH₃ and SO₂ — Ammonia turns red litmus blue whereas sulphur dioxide turns wet blue litmus red and finally bleaches it, though the bleaching is temporary.

Question 4.

Name a gas that :

(a) turns moist starch iodide paper blue black

(b) turns moist red litmus blue

(c) does not affect acidified K₂Cr₂O₇ paper but turns lime water milky.

(d) affects acidified K₂Cr₂O₇ paper and also turns lime water milky.

Answer:

(a) Chlorine

(b) Ammonia

(c) Carbon dioxide

(d) Sulphur dioxide

Question 5.

What do you observe when

(a) CO₂ is passed through lime water first and then a little in excess?

(b) HCl is passed through silver nitrate solution?

(c) H₂S is passed through lead nitrate solution?

(d) Cl₂ is passed through potassium iodide (KI) solution?

(e) Cobalt chloride paper is introduced in water vapour?

Answer:

(a) When CO₂ is passed through lime water first in small amounts it turns lime water milky. This is due to the formation of insoluble calcium carbonate.

Ca(OH)₂ + CO₂ ⟶ CaCO₃ ↓ + H₂O

When excess of the gas is passed through the solution, milkiness disappears. This is due to the formation of a soluble bicarbonate.

CaCO₃ + CO₂ + H₂O ⟶ Ca(HCO₃)₂ [soluble]

(b) When HCl is passed through silver nitrate solution, a white ppt. of silver chloride is formed.

HCl + AgNO₃ ⟶ AgCl ↓ + HNO₃

(c) When H₂S is passed through lead nitrate solution, black ppt. of PbS is formed.

Pb(NO₃)₂ [colourless] + H₂S ⟶ PbS ↓ [black] + 2HNO₃

(d) Cl₂ turns potassium iodide (KI) solution blue black

Cl₂ + 2KI ⟶ 2KCl + I₂

(e) Water vapour turns blue cobalt chloride paper pink.

CoCl₂ + 2H₂O ⟶ CoCl₂.2H₂O

Question 6.

Name:

(a) Two carbonates that do not produce carbon dioxide on heating.

(b) Two nitrates that do not produce nitrogen dioxide on heating.

(c) A brown gas.

(d) A greenish yellow gas.

(e) A gas with rotten egg smell.

Answer:

(a) Sodium carbonate [Na₂CO₃] and Potassium carbonate [K₂CO₃]

(b) Potassium nitrate [KNO₃] and Sodium nitrate [NaNO₃]

(c) Nitrogen dioxide [NO₂]

(d) Chlorine [Cl₂]

(e) Hydrogen sulphide [H₂S]

—  : End of Practical Work Exe-9A Answer Class-9 ICSE Chemistry Solutions :–

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