Sulphur Dioxide

 

Table of Content

Methods to Prepare Sulphur Dioxide Gas Physical Properties of Sulphur Dioxide Chemical Properties of Sulphur Dioxide Identifying Tests for Sulphur Dioxide Gas Structure of Sulphur Dioxide

In the colored particle models, sulphur is yellow and oxygen is red.

 

Fig. 1: Four diverse ways scientists use to demonstrate a particle of sulfur dioxide

Methods to Prepare Sulphur Dioxide Gas

Sulphur dioxide is set up in the laboratory by the activity of dilute sulphuric acid on sulphites

     Na₂SO₃        +       H₂SO₄            → Na₂SO₄                    + H₂O           + SO₂↑
Sodium sulphite         Sulphuric acid      Sodium sulphate      water          Sulphur dioxide

Fig. 2: Laboratory preparation of sulphur dioxide

Commercially, vast volumes of sulphur dioxide are set up by cooking a sulphide ore, for example, iron sulfide. The gas is liquefied subsequent to drying under 25 atm pressure and stored in steel barrels.

Roasting,

Fe₂S₃  +  4O₂         →        FeO +  3SO₂

              Liquefaction 25 atm
So₂ (g)              →                       SO₂(l)

Fig. 3: Industrial preparation of sulphur

Sulphur dioxide is likewise obtained on an extensive scale by blazing sulphur in air.

                           Δ
S        +    O₂      →        SO₂

Physical Properties of Sulphur Dioxide

• Sulphur dioxide is a dull gas with a pungent smell similar to smoldering sulphur.

• It is one of the most straightforward gasses to melt, since it consolidates at room temperature under a pressure of 2 atm.

Chemical Properties of Sulphur Dioxide

• It is an acidic oxide that is readily dissolvable in water.

• It breaks up in water to give sulphurous acid.

       SO₂             +       H₂O     →     H₂SO₃
Sulphur dioxide           Water         Sulphurous acid

• It reacts promptly with sodium hydroxide solution and structures sodium sulphite.

       SO₂             +       2NaOH                   →     Na₂SO₃          + H₂O
Sulphur dioxide            Sodium hydroxide         Sodium sulphate          Water

• In the event that more sulfur dioxide is passed into this arrangement, sodium hydrogen sulphite is framed.

       SO₂             +         Na₂SO₃                   →         H₂O     +         2NaHSO₃  
Sulphur dioxide            Sodium sulphate                      Water           Sodium hydrogen sulphate  
  (excess)

• The sulphur particle in a sulphur dioxide atom is tetravalent. Subsequently, it can augment it's covalency to six by specifically consolidating with elements like O₂ and C_l2 to shape the comparing addition compounds.

Example: It reacts with chlorine within the presence of charcoal as an impetus to give sulphuryl chloride (SO₂Cl₂).

                                                          Charcoal
         SO₂             +           Cl₂                →              SO₂Cl₂
Sulphur dioxide                 Chlorine       (Catalyst)      Sulphuryl Chloride

• Within the sight of vanadium pentoxide as an impetus, it gives sulphur trioxide.

                                                              V₂O₅
         2SO₂             +           O₂                →              SO₃
Sulphur dioxide                 Oxygen                           Sulphur trioxide

• Within the sight of moisture, it can start giving nascent oxygen, and, along these lines, go about as a reducing agent.

Example: It reduces ferric salts to ferrous salts, and halogens to halogen acids.

 2Fe³⁺  +  SO₂     + 2H₂O     →   2Fe²⁺     +  SO₄^2-   +   4H⁺
Ferric     Sulphur       water           Ferrous
   salt        dioxide                               salt
X₂           +   SO₂     + 2H₂O     →   SO₄^2-     +  2X ^-   +   4H⁺
Halogen     Sulphur       water                                   halogen
                     dioxide                                                   acid

Identifying Tests for Sulphur Dioxide Gas

• It decolorizes acidified KMnO₄ solution

    5SO₂     + 2KMnO₄       + 2H₂O  → K₂SO₄     +      2 MnSO₄ + 2H₂SO₄
Sulphur       potassium                       potassium       Manganese       Sulphuric
dioxide       permanganate                     sulphate            sulphate           acid

• It turns a filter paper moistened with acidified K₂Cr₂O₇ solution green

    3SO₂     +   K₂Cr₂O₇       +    H₂SO₄          →  K₂SO₄     +      2Cr₂(SO₄)₃ +     H₂O
Sulphur       Potassium            Sulphuric             potassium        chromium      
dioxide           dichromate               acid               sulphate            sulphate      

• It turns starch iodate paper blue

   5SO₂   +    2KIO₃   +  4H₂O →  2KHSO₄     +   3H₂SO₄     +   I₂
Sulphur     potassium     Water      potassium       Sulphuric        Iodine
 dioxide        iodate                       hydrogen            acid
                                                     sulphate

Structure of Sulphur Dioxide

It is angular shaped with an O-S-O bond edge of 119.50. Take note of that despite the fact that sulphur dioxide has two unique sorts of pi bonds, i.e. p pi - p pi and d pi - p pi.

The two sulphur-oxygen bond lengths are equivalent. This shows sulphur dioxide is a resonance hybrid of two canonical structures.

Fig. 4: Resonance forms of sulphur dioxide

 

Fig. 5: Bond angle of sulphur dioxide

 

Uses:

The different uses of sulphur dioxide are:

1) In the assembling of sulphites, sulphuric acid,  and hydrogen sulphite.

2) In the sugar business, for refining and decolorizing sugar.

3) For refining lamp oil, and other petroleum items.

4) As a disinfectant.

5) As a fumigant.

6) For dying fragile articles.

7) As antichlor, to expel the overabundance chlorine from substances those have been faded by chlorine.

8) As a glue solvent.

9) As a refrigerant in refrigerators.

10) As an additive for wines, meat, dry natural products and so on.

Fig. 6: Summary of the uses of sulphur

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Sulphur Dioxide