JEE Main · 2020 · 04 Sep 2020 · Shift 2 · d and f Block Elements

The tungsten statement is correct, since $\mathrm{W}(\mathrm{VI})$ is indeed more stable than $\mathrm{Cr}(\mathrm{VI})$, the higher oxidation state becoming more stable down a transition-metal group. The lanthanoid statement is also correct, as oxides such as europium-doped yttrium oxide serve as phosphors. The remaining claim is wrong: in the presence of $\mathrm{HCl}$ the permanganate oxidises chloride to chlorine, consuming extra oxidant and spoiling the titration, so it does not give satisfactory results. Thus the only incorrect statement is the one about permanganate titrations in $\mathrm{HCl}$.