Question: why pbcl4 is unstable to heat?
Answer: (a) Lead (II) chloride reacts with Cl2 to give PbCl4. (b) Lead (IV) chloride is highly unstable towards heat. (c) Lead is known not to form an iodide PbI4. (i) This is because lead is more stable in +2 oxidation state than in +4 oxidation state due to inert pair effect.