Give uses of Borax. 

The crystalline form of borax has

($A$) tetranuclear $\left[\mathrm{B}_4 \mathrm{O}_5(\mathrm{OH})_4\right]^{2-}$ unit

($B$) all boron atoms in the same plane

($C$) equal number of $s p^2$ and $s p^3$ hybridized boron atoms

($D$) one terminal hydroxide per boron atom

Which does not show inert pair effect ?

The element which exists in liquid state for a wide range of temperature and can be used for measuring high temperature is :- 

Compare $\pi  - $ bond strength between $B$ and $N$ given in two compounds

$(I)$ $\begin{array}{*{20}{c}}
{{{\left( {C{H_3}} \right)}_3}Si - NB{H_2}}\\
{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|}\\
{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,Si{{(C{H_3})}_3}}
\end{array}$     $(II)$ $\begin{array}{*{20}{c}}
{{{\left( {C{H_3}} \right)}_3}C - NB{H_2}}\\
{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|}\\
{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,C{{(C{H_3})}_3}}
\end{array}$

Purification of aluminium done by electrolytic refining is known as