Question

Give reasons:-

(i) Lead(IV) chloride is highlt unstable towards heat.

(ii) Lead is known not to form iodide, PbI₄

Answer 1

1) ) Pb belongs to 14 group.The two oxidation states displayed by this group is +2 and +4. On moving down the group, the +2 oxidation state becomes more stable and the +4 oxidation state becomes less stable the higher oxidation state becomes less stable due to inert pair effect.Therefore, PbCl₄ decomposes to form more stable PbCl₂ on heating.
PbCl₄(l) ∆ → PbCl₂(s) + Cl₂(g)

2) Halide ions are reducing agents and their reducing power increases in the order: F^- < Cl^- < Br^- < I^-
I^- ion being a strong reducing agent, reduces Pb⁴⁺ to Pb²⁺ and oxidizes itself to I₂.Therefore, lead is known not to form PbI₄ .
PbI₄ → PbI₂ + I₂
unstable