JEE Main · 2024 · 29 Jan 2024 · Shift 1 · d and f Block Elements

In the chromyl chloride test, ${\text{Cl}}^{-}$ with ${\text{K}}_2{\text{Cr}}_2{\text{O}}_7$ and conc. ${\text{H}}_2{\text{SO}}_4$ forms orange ${\text{CrO}}_2{\text{Cl}}_2$ vapour, which dissolves in NaOH to give a yellow chromate (${\text{CrO}}_4^{2-}$) solution.

On acidification, extraction with amyl alcohol, and treatment with $10\%{\text{H}}_2{\text{O}}_2$, chromium pentoxide ${\text{CrO}}_5$ forms in the organic layer as a blue compound. In ${\text{CrO}}_5$, chromium has two peroxo (${\text{O}}_2^{2-}$) linkages and one oxo linkage, giving it an oxidation state of $+6$.

Key confirmed: A (+6).