Question

Making use of only substances chosen from those given below:

Dilute Sulphuric acid, Sodium carbonate, Zinc, Sodium sulphite, Lead, Calcium carbonate

Give the equations for the reactions by which you could obtain

Sulphor dioxide

Answer 1

• The reaction between dil Sulphuric acid and Sodium sulphite occurs in two steps and is a double replacement reaction is takes place here.
• In the first step Sulphuric acid reacts with Sodium sulphite to give Sodium sulphate and sulphurous acid.

H₂SO₄ (aq)+ Na₂SO₃(s) ⇢ Na₂SO₄ (s) + H₂SO₃ (aq)

• In the second step, Sulphurous acid which is highly unstable decomposes into Sulphur dioxide and water.

H₂SO₃ (aq) ⇢ SO₂ (g) + H₂O(aq)

• Thus the overall reaction is

H₂SO₄ (aq) + Na₂SO₃ (s) ⇢ Na₂SO₄ (s)+ SO₂ (g)+ H₂O (aq)