On heating pyrolusite with $KOH$ in the presence of air,we get:

Which one of the following species does not represent a cationic species of vanadium formed in an aqueous solution?

$X$ is an oxoanion of the lightest element of group $7$ in the periodic table. The metal is in $+6$ oxidation state in $X$. The color of the potassium salt of $X$ is

The yellow colour of chromates changes to orange on acidification due to the formation of:

Which from the following alloys is used in gas turbine engines?

Mark the correct statements.