Explain structures of diborane and boric acid.
$(a)$ Diborane is an electron deficient compound in which only $12$ valence electrons are present. $2 B$ atoms and $4$ terminal $H$ atoms are co-planar whereas two bridging hydrogen are present in perpendicular plane. One bridging hydrogen is above the plane and other bridging $H$ atom is below the plane. Terminal $B - H$ bonds are $2 c -2 e$ bonds and bridging $B - H - B$ bonds are $3 c$ $-2 e$ bonds.
$(b)$ Boric acid has layered structure. Planar $BO _3$ unit is linked to another unit through $H$ atoms. The $H$ atoms form covalent bond with $BO _3$ unit and hydrogen bond with other $BO _3$ unit.
The $+1 -$ oxidation state in group $-13$ and $+2$ oxidation state in group $-14$ becomes more and more stable with increasing atomic number. Explain.
Give uses of $LiBH_4$ and $NaBH_4$.
The bond dissociation energy of $B- F$ in $BF_3$ is $646 \,kJ\, mol^{-1}$ whereas that of $C - F$ in $CF_4$ is $515\, kJ\, mol^{-1}.$ The correct reason for higher $B- F$ bond dissociation energy as compared to that of $C-F$ is
Anhydrous $ALCl_3$ is covalent however,when it is dissolved in water hydrared ionic species are formed. This transformation is owing to
Aluminium trifluoride is insoluble in anhydrous $HF$ but dissolves on addition of $NaF$. Aluminium trifluoride precipitates out of the resulting solution when gaseous $BF_3$, is bubbled through. Give reasons.