Which lanthanoid compound is used in pigments?

Which of the following exhibits the maximum oxidation state of vanadium?

Acidified potassium permanganate solution oxidises oxalic acid. The spin-only magnetic moment of the manganese product formed from the above reaction is $.... \, B.M.$ (Nearest Integer)

What is the starting material for the preparation of $KMnO_4$?

Select the salt whose aqueous solution is not green.

Among $Co^{3+}$,$Ti^{2+}$,$V^{2+}$ and $Cr^{2+}$ ions,one if used as a reagent cannot liberate $H_{2}$ from dilute mineral acid solution,its spin-only magnetic moment in gaseous state is $.....$ $B.M.$ (Nearest integer)