JEE MainChemistryp Block Elements (Group 13 & 14)
Based on the relative stability of oxidation states due to the inert pair effect, which of the following redox reactions is thermodynamically spontaneous in the forward direction?
Options
- APb ²⁺ + Sn ⁴⁺ Pb ⁴⁺ + Sn ²⁺
- BTl ⁺ + In ³⁺ Tl ³⁺ + In ⁺
- CSn ²⁺ + Ge ⁴⁺ Sn ⁴⁺ + Ge ²⁺
- DPb ⁴⁺ + Sn ²⁺ Pb ²⁺ + Sn ⁴⁺
Correct answer
D. Pb ⁴⁺ + Sn ²⁺ Pb ²⁺ + Sn ⁴⁺
Step-by-step solution
Due to the inert pair effect, the stability of the lower oxidation state (+2) increases down Group 14, while the stability of the higher oxidation state (+4) decreases. Therefore, Pb ²⁺ is more stable than Pb ⁴⁺ , and Sn ⁴⁺ is more stable than Sn ²⁺ . As a result, Pb ⁴⁺ acts as a strong oxidising agent and readily accepts electrons to become Pb ²⁺ , while Sn ²⁺ acts as a reducing agent and loses electrons to become Sn ⁴⁺ . The spontaneous reaction is thus the oxidation of Sn ²⁺ by Pb ⁴⁺ : Pb ⁴⁺ + Sn ²⁺ Pb ²⁺ + Sn ⁴