Question

(i)

Sulphur dioxide acts as an oxidizing agent as well as a reducing agent. Give one reaction each to show its oxidizing nature and its reducing nature.
(ii)

Explain why an aqueous solution of potassium hexacyanoferrate (II) does not give the test for ferrous ion.

Answer 1

(i)

1. SO₂ as an oxidising agent
2Mg + SO₂ → 2MgO + S
(Burning)
2. SO₂ as a reducing agent
SO₂ + Br₂ + 2H₂O → H₂SO₄ + 2HBr

(ii)

Potassium hexacyanoferrate (II) does not give ferrous (Fe²⁺) ions in solution because it is complex and Fe²⁺ ions are in the coordination sphere and form coordinate bonds with cyanide, CN^– ligands.