TN State Board 12th Chemistry Question Paper 2026

Sodium is extracted by an electrochemical process, namely electrolysis of molten sodium chloride (Downs process). Iron, silver and lead are generally extracted by chemical reduction or other metallurgical methods, not by electrolysis in their usual extraction routes.

The stability of the $+1$ oxidation state increases down group 13 due to the inert pair effect. Thus the order is $\mathrm{Tl > In > Ga > Al}$, i.e. $\mathrm{Tl < In < Ga < Al}$ in increasing stability. Hence option D is correct.

$\mathrm{XeF_6}$ on complete hydrolysis gives xenon trioxide. The overall reaction is: $$\mathrm{XeF_6 + 3H_2O \rightarrow XeO_3 + 6HF}$$ So the correct product is $\mathrm{XeO_3}$. The other oxyfluorides are formed only in partial hydrolysis.

The incorrect statement is D. A large negative standard electrode potential means the metal is easily oxidised, so it acts as a powerful reducing agent, not an oxidising agent. A is correct because $\mathrm{Co^{3+}}$ is $d^6$ and low-spin octahedral, while $\mathrm{Fe^{2+}}$ is also $d^6$; in many common cases they are compared as having the same number of unpaired electrons. B is correct: silver has the highest electrical conductivity at room temperature. C is correct for substitutional alloys, where the atomic size difference should generally be less than 15%.

$[\mathrm{Pt(Py)(NH_3)(Br)(Cl)}]$ is a square planar complex of the type $\mathrm{MA_2BC}$ (all ligands different except the two positions occupied by none repeated? here effectively four different ligands around Pt). For square planar complexes with four different ligands, geometrical isomerism arises from different relative positions of pairs of ligands. The number of distinct arrangements is 3, corresponding to choosing which one is trans to a given ligand. Hence the correct answer is 3.