[5 Mark Question Answer]

Question 15 Marks

Complete the following table and write your observations.

	Hydrogen sulphide	Ammonia	Sulphur dioxide	Hydrogen chloride
Shake the gas with red litmus solution
Shake the gas with blue litmus solution
Apply a burning splint to a gas

Answer

	Hydrogen sulphide	Ammonia	Sulphur dioxide	Hydrogen chloride
Shake the gas with red litmus solution	No change in the colour of litmus solution	Red litmus solution becomes blue in colour.	No change in the colour of litmus solution	No change in the colour of litmus solution
Shake the gas with blue litmus solution	Blue litmus solution becomes red in colour.	No change in the colour of blue litmus solution.	Blue litmus solution becomes red in colour.	Blue litmus solution becomes red in colour
Apply a burning splint to a gas	No reaction.	No reaction.	No reaction.	No reaction.

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Question 25 Marks

(a) Give only one suitable chemical test to identify the following gases.

Ammonia
Sulphur dioxide
Hydrogen Chloride
Chlorine
Carbon Dioxide
Oxygen
Hydrogen

(b) Select a basic gas mentioned in Q.1 (a). How is the basic nature suspected?(c)Select acidic gases from the gases mentioned in Q.1 (a). How is the acidic nature suspected?
(d) State the gas responsible for bleaching action.
(e)Which gas turn blue cobalt chloride paper light pink?

Answer

(a) (i) Chemical test for ammonia:
If a rod dipped in concentrated hydrochloric acid is brought near ammonia gas, dense white fumes of ammonium chloride $\left(\mathrm{NH}_4 \mathrm{Cl}\right)$ are formed.
(ii) Chemical test for Sulphur dioxide:
It decolorizes pink coloured potassium permanganate solution.
$2 \mathrm{KMnO}_4+2 \mathrm{H}_2 \mathrm{O}+5 \mathrm{SO}_2 \longrightarrow \mathrm{K}_2 \mathrm{SO}_4+2 \mathrm{MnSO}_4+2 \mathrm{H}_2 \mathrm{SO}_4$
(iii) Chemical test for $\mathrm{HCl}$ :
When $\mathrm{HCl}$ gas is passed through $\mathrm{AgNO}_3$ solution, white precipitates of $\mathrm{AgCl}$ are formed which gets dissolved in excess of $\mathrm{NH}_4 \mathrm{OH}$.
$\mathrm{AgNO}_3(\mathrm{aq})+\mathrm{HCl} \longrightarrow \mathrm{AgCl} \downarrow+\mathrm{HNO}_3$
(iv) Chemical test for Chlorine:
It turns moist starch iodide paper (KI + starch solution) blue-black.
(v) Chemical test for Carbon dioxide:
When this gas is passed through lime water, it turns milky due to the formation of white precipitates of $\mathrm{CaCO}_3$ and on passing excess of carbon dioxide gas, this milkiness disappears.
(vi) Chemical test for oxygen:
This gas is absorbed in a colourless alkaline solution of pyrogallol and turns it dark brown.
(vii) Chemical test for hydrogen:
It burns with a pop sound when a burning taper is brought near it.
(b)Ammonia is a basic gas and its basic nature is suspected through litmus paper test because it changes the colour of red litmus paper to blue.
(c) Chlorine, carbon dioxide, hydrogen chloride, hydrogen sulphide and sulphur dioxide are acidic gases since they convert blue litmus to red.
(d) Chlorine gas.
(e) Water vapour.C

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CHEMISTRY [5 Mark Question Answer]

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