Reaction of liquid SO2


Reaction of liquid SO2

Introduction of liquid SO2:

Liquid SO2 is non-protonic solvents, because it cannot give proton on self-ionization. Under normal temperature the pressure, Sulphur dioxide is a gas but can be liquefied. It has a wide liquid range from -10.0oC to -75.5oC and hence can be used as solvents. Its dielectric constant is low (=17.4 at -20oC) and hence it is a poor solvent for covalent compounds.

Definition of liquid SO2:

     Sulphur dioxide is the chemical compound with the formula SO2. It is a toxic gas responsible for the smell of burnt matches. It is released naturally by volcanic activity and is produced as a byproduct of copper extraction and the burning of fossil fuels contaminated with Sulfur compounds.


Formula of Sulphur dioxides is SO2.


Its IUPAC name is Sulfur dioxide.

Boiling point:

Boiling point of Sulphur Dioxide is -10 o C

Melting point:

Melting point of Sulphur Dioxide is -75.5o C

Soluble in:

Sulphur dioxide is soluble in Water.

Solubility of various substances in liquid SO2:

Some compounds and substances are soluble in liquid Sulphur dioxide. Their reaction with liquid SO2 is given below;

  • Solubility of ionic compounds

  • Solubility of non-ionic compounds

  • Solubility of metals

  • Solubility of ionic compounds:

Iodides and thiocyanates are the most soluble. Sulphates, sulphides, oxides and hydroxides are practically insoluble. May of the ammonium, thallium and mercuric salts are soluble.

  • Solubility of non-ionic compounds:

Covalent halides like ammines, ether, alcohols, benzene, alkanes, pyridine, quinolone, halogen derivatives and acid chlorides are soluble. Alkanes are insoluble.

  • Solubility of Metals:

Metals are insoluble in liquid SO2.

Auto-ionization of liquid SO2:

When we compare the self-ionization of liq.SO2 with that of water and liq.NH3, we find that SO2 ion is analogous to NH4 ion while SO32-ion in analogous to OH- and NH2- ion is produce by the self-ionization of H2O and liq.NH3 respectively. Thus all those compounds which contain or make available SO2+ ions will act as acids in liq.SO2. Similarly all those compounds which contain or make available SO32- ions, will behave as bases in liq.SO2.

Self-ionization of liquid SO2 takes place as follows:

SO2 SO2+ + O2-  

SO2 + O2-  SO32-

SO2 + SO2 SO2++ SO32-

The SO2 give SO2+ ion in liq.SO2, they behave as acids in this solvent. On the other hand, the substances, SO2 and O2- which give SO32- ion in this solvent act as bases.

Structure of liquid Sulphur dioxide:

This compound is a bent molecule and has a bond order of 1.5. The resonance structure can be described using the valence bond theory using s and p orbitals.

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