Manganese achieves its highest oxidation state in which of the following compounds?

The starting material for the manufacture of $KMnO_4$ is

Which among the following statements is incorrect for interstitial compounds?
$1$. They are very hard and rigid
$2$. They have higher melting point than pure metal
$3$. They do not show conductivity
$4$. They are chemically inert

If an oxide of manganese has a value of magnetic moment $( \mu )$ of $4.9 \ BM$,then which oxide would it be?

When a mixture of manganese dioxide,potassium hydroxide and potassium chlorate is fused,the product obtained is

The spin-only magnetic moment value of the most basic oxide of vanadium among $V_2O_3$,$V_2O_4$,and $V_2O_5$ is $..... \ B.M.$ (Nearest Integer).