Hydrogen sulphide is prepared by reacting iron (II) sulphide dilute hydrochloric acid

FeS (s)  + 2HCl (aq)  ->  H₂S (g)  FeCl₂ (aq)

PHYSICAL PROPERTIES 0F H₂S

- Hydrogen sulphide is a colourless gas with characteristic pungent poisonous smell of rotten eggs

-  It is soluble in cold water but insoluble in warm water

-  It is denser than water and turns blue litmus paper red.

CHEMICAL PROPERTIES OF H₂S

1.When hydrogen sulphide is bubbled in a metallic salt solution, a metallic sulphide is formed.

All sulphides are insoluble black salts except sodium sulphide, potassium sulphide and ammonium sulphides.

Hydrogen sulphide gas blackens moist Lead (II) ethanoate /Lead (II) nitrate(V) paper .

The gas reacts with Pb²⁺ in the paper to form black Lead(II)sulphide.

Pb²⁺_(aq)   + H₂S   -> PbS(s)    + 2H⁺(aq)

2.Hydrogen sulphide burns in excess air with a blue flame to form sulphur(IV)oxide gas and water.

Chemical equation:2H₂S(g)+ 3O_2(g)  -> 2H₂O(l) +2SO₂ (g) 

Hydrogen sulphide burns in limited air with a blue flame to form sulphur solid and water.

Chemical equation: 2H₂S(g)+ O₂ (g) ->   2H₂O(l) +   2S(s)

3. Hydrogen sulphide gas reduces acidified potassium dichromate(VI) from orange Cr₂O_7²⁺ ions to green Cr³⁺ ions leaving a  yellow solid residue as itself is oxidized to sulphur.

Chemical/ionic equation:

4. H₂S (aq) +Cr₂O_7^2- (aq)+6H⁺ (aq)-> 4S(aq)+2Cr³⁺ (aq) +7H₂O(l)

This test is used for differentiating Hydrogen sulphide and sulphur (IV)oxide gas.

Sulphur(IV)oxide also reduces acidified potassium dichromate(VI) from orange Cr2O72- ions to green Cr3+ ions without leaving a yellow residue.

4. Hydrogen sulphide gas reduces acidified potassium manganate(VII) from purple MnO4- ions to green Mn2+ ions leaving a yellow residue as the gas itself is oxidized to sulphur.

Chemical/ionic equation:

5. H₂S(g)  +   2MnO^4- (aq) +6H⁺ (aq)   -> 5S (s) +  2Mn²⁺ (aq) +  8H₂O(l)

5. Hydrogen sulphide gas reduces yellow bromine water to colourless hydrobromic acid (HBr) leaving a yellow residue as the gas  itself is oxidized to sulphur.

Chemical/ionic equation:

H₂S (g)  +   Br₂ (aq)   ->    S (s)    +       2HBr(aq)

          (yellow solution)    (yellow solid)        (colourless)

6. Hydrogen sulphide gas reduces Iron (III)chloride solution to green Fe2+ ions leaving a yellow  residue.

The gas is  itself oxidized to sulphur.

H₂S (aq)  +  2Fe³⁺ (aq) -> S (s) +  Fe²⁺ (aq) +  2H⁺ (aq)

  (yellow solution)  (yellow residue)    (green)

7. Hydrogen sulphide gas reduces concentrated nitric(V)acid to brown nitrogen(IV)oxide gas itself oxidized to yellow sulphur.

Chemical/ionic equation:

H₂S (g) +  2HNO₃ (l)->  2H₂O(l) + S (s) + 2NO₂ (g)

                                                               (brown fumes)

8. Hydrogen sulphide gas reduces concentrated sulphuric(VI)acid to yellow sulphur.

Chemical/ionic equation:

3H₂S(g) +  H₂SO₄ (l)  ->  4H₂O(l)   +   4S (s)   (yellow residue)

Hydrogen sulphide gas reduces 20 volume hydrogen peroxide to water and  itself oxidized to yellow sulphur

Chemical/ionic equation:

H₂S (g) +  H₂O₂ (l)  ->     2H₂O(l)   +   S (s)  

                                                    (yellow residue)

1. which is the most dominant property of H₂S

2. which method is the most suitable for collection of H₂S

3. how can you differentiate hydrogen sulphide with sulpher (IV) oxide gas

4. What will happen when the two gases are mixed