Write balanced chemical equations to show –

(i) The oxidizing action of conc. sulphuric acid on carbon.

(ii) The behaviour of H₂SO₄ as an acid when it reacts with magnesium.

(iii) The dehydrating property of conc. sulphuric acid with sugar.

(iv) The conversion of SO₃ to sulphuric acid in the Contact process.

(i) C + 2H₂SO₄ (conc.) ⟶ CO₂ + 2SO₂ + 2H₂O

(ii) Mg + H₂SO₄ (dil.) ⟶ MgSO₄ + H₂ (g)

(iii) $\text{C}${12}\text{H}{22}\text{O}{11}\xrightarrow{\text{Conc. H}2\text{SO}4} \text{12C} \small{\space[sugar\space charcoal]} + \text{11H}2\text{O}

(iv) SO₃ + H₂SO₄ (conc.) ⟶ H₂S₂O₇ (oleum)
H₂S₂O₇ + H₂O ⟶ 2H₂SO₄ (conc.)