Which reactions can be used to prepare diborane?
$I.$ $3NaBH_4 + 4BF_3 \xrightarrow{\text{ether}} 2B_2H_6 + 3NaBF_4$
$II.$ $2NaBH_4 + I_2 \to B_2H_6 + 2NaI + H_2$
$III.$ $2BF_3 + 6NaH \xrightarrow{450 \ K} B_2H_6 + 6NaF$

Which of the following statements about $BF_4^{-}$ and $AlF_6^{3-}$ are correct?
$(i)$ $B$ and $Al$ differ in their oxidation states.
$(ii)$ $B$ and $Al$ differ in their covalency.
$(iii)$ $B$ obeys the octet rule.
$(iv)$ $B$ and $Al$ are in diagonal relationship.

When borax is heated with $CoO$ on a platinum loop,the blue coloured bead formed is largely due to

Which of the following compounds of boron does not exist in the free form?

In the reaction $B_2O_3 + C + Cl_2 \to A + CO$,the $A$ is:

Aluminium is a self-protecting metal,because