Question 15 Marks
(a) Give only one suitable 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 suspected?
(c) Select acidic gases from the gases mentioned in Q .1 (a). How is the acidic nature suspected?
(d) The two gases $A$ and $B$ are bleaching agents. $A$ is greenish-yellow and bleaches due to its oxidizing property while $B$ is a colourless gas that bleaches due to reduction. Identify $A$ and $B$ ?
(e) Which gas turn blue cobalt chloride paper light pink?
Give one similarity in the test between (i) $Cl _2$ and HCl (ii) $SO _2$ and $CO _2$.
(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 suspected?
(c) Select acidic gases from the gases mentioned in Q .1 (a). How is the acidic nature suspected?
(d) The two gases $A$ and $B$ are bleaching agents. $A$ is greenish-yellow and bleaches due to its oxidizing property while $B$ is a colourless gas that bleaches due to reduction. Identify $A$ and $B$ ?
(e) Which gas turn blue cobalt chloride paper light pink?
Give one similarity in the test between (i) $Cl _2$ and HCl (ii) $SO _2$ and $CO _2$.
Answer
View full question & 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 $(NH_4Cl)$ are formed.
(ii) Chemical test for Sulphur dioxide:
It decolorizes pink coloured potassium permanganate solution.
$2 KMnO _4+2 H _2 O +5 SO _2 \longrightarrow K _2 SO _4+2 MnSO _4+2 H _2 SO _4$
(iii) Chemical test for HCl:
When HCl gas is passed through $AgNO_3$ solution, white precipitates of AgCl are formed which gets dissolved in excess of $NH_4OH.$
$AgNO _3( aq )+ HCl \longrightarrow AgCl \downarrow+ HNO _3$
(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 $CaCO_3$ and on passing excess of carbon dioxide gas, this milkiness disappears.
(vi) Chemical test for oxygen:
This gas is absorbed in 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) A is chlorine and B is Sulphur dioxide.
(e) Water vapour.
(i) Chemical test for ammonia:
If a rod dipped in concentrated hydrochloric acid is brought near ammonia gas, dense white fumes of ammonium chloride $(NH_4Cl)$ are formed.
(ii) Chemical test for Sulphur dioxide:
It decolorizes pink coloured potassium permanganate solution.
$2 KMnO _4+2 H _2 O +5 SO _2 \longrightarrow K _2 SO _4+2 MnSO _4+2 H _2 SO _4$
(iii) Chemical test for HCl:
When HCl gas is passed through $AgNO_3$ solution, white precipitates of AgCl are formed which gets dissolved in excess of $NH_4OH.$
$AgNO _3( aq )+ HCl \longrightarrow AgCl \downarrow+ HNO _3$
(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 $CaCO_3$ and on passing excess of carbon dioxide gas, this milkiness disappears.
(vi) Chemical test for oxygen:
This gas is absorbed in 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) A is chlorine and B is Sulphur dioxide.
(e) Water vapour.