Which gas makes sulphurus acid when mixed with water 

CONCEPT:

Formation of Sulphurous Acid

• Sulphurous acid (H₂SO₃) is formed when sulfur dioxide (SO₂) gas is dissolved in water.
• The chemical reaction can be represented as:

  SO₂(g) + H₂O(l) → H₂SO₃(aq)

• Sulphurous acid is a weak acid and exists in equilibrium with dissolved sulfur dioxide in aqueous solution.

EXPLANATION:

• 1) PH₃: Phosphine gas does not react with water to form sulphurous acid.
• 2) SO₂: Sulfur dioxide reacts with water to form sulphurous acid (H₂SO₃).
• 3) H₂S: Hydrogen sulfide does not form sulphurous acid upon mixing with water.
• 4) N₂: Nitrogen gas is inert and does not react with water under normal conditions.

The correct answer is SO₂.

Therefore, SO₂ gas forms sulphurous acid when mixed with water.