What is SO2? Important knowledge about SO2.

1. Definition of SO₂
   1.1. Names
   1.1.1. Common name: Sulfur dioxide, sometimes also referred to as sulfur gas.
   1.1.2. English name: Sulfur dioxide.
   1.2. Atomic mass: SO₂ has an atomic mass of 64.066 (32.065 for S and 15.9994 x 2 for O).
   1.3. Atomic structure: An SO₂ molecule contains 1 sulfur atom and 2 oxygen atoms.
   1.4. Ion structure: SO₂ does not dissociate into ions in water solution.

2. Properties of SO₂
   2.1. Physical properties of SO₂: SO₂ is a colorless gas with a strong, distinctive smell. It is quite toxic and irritating to the eyes and respiratory tract. In water solution, SO₂ creates an acidic environment (pH < 7).
   2.2. Chemical properties of SO₂: SO₂ has the ability to oxidize and reduce, it can react with water to form sulfurous acid (H₂SO₃) and react with oxygen to form SO₃.

3. Common chemical reactions of SO₂
   SO₂ does not react with metals and salts. However, it can react with acids and non-metals as follows:

3.1. Acid reaction: SO₂ + H₂O -> H₂SO₃
3.2. Non-metal reaction: 2SO₂ + O₂ -> 2SO₃

4. Synthesis of SO₂
   4.1. Laboratory synthesis of SO₂: SO₂ can be synthesized by burning sulfur in air or oxygen.
   4.2. Industrial synthesis of SO₂: In industry, SO₂ is commonly produced by burning sulfur or pyrite (FeS₂) in air.