Which of the following ores is used for the production of $K_2Cr_2O_7$?

Superconductors are derived from compounds of

The spin only magnetic moment $(\mu)$ value $(B.M.)$ of the compound with strongest oxidising power among $Mn_2O_3$,$TiO$,and $VO$ is $....$ $B.M.$ (Nearest integer).

The alloy that contains copper and $Zn$ is $x$ and the one that contains copper and $Ni$ is $y$. What are $x$ and $y$ respectively?

Which pair of elements from the following is used to make an alloy for trophies?

$A$ purple colored compound of Manganese $(X)$ decomposes on heating to liberate oxygen and forms compounds of Manganese $(Y)$ and $(Z)$. Compound $(Z)$ reacts with $KOH$ in the presence of potassium nitrate to give compound $(Y)$. Compounds $(X)$,$(Y)$,and $(Z)$ respectively are: