Describe laboratory method of preparation of sulphur dioxide giving chemical equations. Give chemical equations of the reactions of sulphur dioxide with potassium permanganate and lime water.

The laboratory preparation of sulfur dioxide (SO₂) can be achieved through the combustion of sulfur in the presence of oxygen. This method is straightforward and involves a few key steps.

Preparation of Sulfur Dioxide

To prepare sulfur dioxide, sulfur is burned in an excess of oxygen. The chemical equation for this reaction is:

S + O₂ → SO₂

In this reaction, sulfur (S) reacts with oxygen (O₂) to produce sulfur dioxide (SO₂). This process typically occurs in a fume hood due to the toxic nature of the gas produced.

Reactions of Sulfur Dioxide

Once sulfur dioxide is prepared, it can react with various substances. Here are two notable reactions:

• Reaction with Potassium Permanganate:

  Sulfur dioxide acts as a reducing agent when it reacts with potassium permanganate (KMnO₄) in an acidic medium. The equation for this reaction is:

  5 SO₂ + 2 KMnO₄ + 2 H₂SO₄ → 5 S + 2 MnSO₄ + K₂SO₄ + 2 H₂O

• Reaction with Lime Water:

  When sulfur dioxide is bubbled through lime water (a solution of calcium hydroxide), it reacts to form calcium sulfite. The equation is:

  SO₂ + Ca(OH)₂ → CaSO₃ + H₂O

These reactions illustrate the chemical behavior of sulfur dioxide in different environments, showcasing its role as both a reducing agent and an acid.