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Identification of Gases

Gas Test

1.Hydrogen

(H2)

  • Burns with pale blue flame producing a 'pop' sound
  • Extinguishes burning splinter.
  • Neutral to Litmus
  • Colourless, Odourless

2.Oxygen

(O2)

  • Colourless alkaline pyrogallol solution turns brown.
  • Rekindles a glowing wooden splinter
  • Neutral to litmus.
  • Colourless, Odourless.

3.Carbon     dioxide

(CO2)

  • Extinguishes burning splinter.
  • Turns lime water Ca(OH)Milky.
  • No effect on acidified KMnO4 & K2Cr2O7 solution.
  • Moist litmus turns faint red.
  • Colourless, Odourless

4.Sulphur    dioxide

(SO2)

  • Extinguishes burning splinter.
  • Turns acidified KMnO4 solution pink to clear colourless.
  • Turns acidified K2Cr2O7 solution orange to clear green.
  • Moist litmus turns red.
  • Colourless & Suffocating smell.
5.Chlorine (Cl2)
  • Turns moist starch iodide paper blue black.
  • Turns moist blue litmus red & then bleaches it.
  • Greenish yellow & Pungent smell.

6.Hydrogen chloride

(HCl)

  • Give dense white fumes with ammonia.
  • Gives curdy white ppt with AgNO3 solution.
  • Turns moist blue litmus red.
  • Colourless & Pungent smell.

7.Hydrogen sulphide

(H2S)

  • Turns acidified KMnO4 solution pink to colourless.
  • Turns acidified K2Cr2O7 solution orange to  green.
  • Turns moist lead acetate paper silvery black.
  • Turns moist blue litmus red.
  • Colourless & Rotten egg smell.

8.Nitrogen dioxide

(NO2)

  • Turns potassium iodide paper brown & liberate violet vapours of iodine.
  • Turns moist blue litmus red.
  • Reddish brown & Irritating smell.
9.Ammonia (NH3)
  • Gives dense white fumes with HCl
  • Give pale blue ppt with CuSO4 solution.
  • Turns Nessler's reagent (potassium mercuric iodide) pale brown or give a reddish brown ppt.
  • Colourless & Pungent smell
10. Water          Vapour
  • Turns white anhydrous copper sulphate blue.
  • Turn blue cobalt chloride paper pink.
  • Neutral to liymus
  • Colourless, Odourless

 

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