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)

Indicate the steps in the preparation of:
$(i)$ $K_2Cr_2O_7$ from chromite ore.
$(ii)$ $KMnO_4$ from pyrolusite ore.

Fill in the blanks:
$(1)$ In the dichromate ion,the $O-Cr-O$ bond angle is ....... $^o$.
$(2)$ The reaction $3Sn^{2+} \to 3Sn^{4+} + 6e^-$ occurs via .........,in which $Sn^{2+}$ is ......... .
$(3)$ The symbols for stannous and stannic are ......... and ......... respectively.
$(4)$ $V_2O_4$ dissolves in acidic compounds to give ......... salts.

Thermal decomposition of a $Mn$ compound $(X)$ at $513 \ K$ results in compound $Y$,$MnO_2$ and a gaseous product. $MnO_2$ reacts with $NaCl$ and concentrated $H_2SO_4$ to give a pungent gas $Z$. Identify $X, Y$ and $Z$.

When a manganese $(Mn^{II})$ salt is fused with a mixture of $KNO_3$ and solid $NaOH$,what will be the oxidation state of $Mn$ after it changes from $+2$?

The transition metal which forms a green compound in $+3$ oxidation state and a yellow-orange compound in $+6$ oxidation state is