Explain the following :
(a) Aluminium vessel can be used to store `conc HNO_(3)`.
(b) `AlCl_(3)` forms a dimer, but `BCl_(3)` does not.
( c) `Al` metal is frequency used as a reducing agent for the extraction of metal such as `Cr`, etc.
(d) `Al` cannot be prepared by the electrolysis of aqueous solution of its salt.
( e) The `B-X` distance is shorter than what is expected theoretically in `BX_(3)` molecule `(X = F, Cl, Br, I)`.
(f) Althrough the ionisation potential of `B(8.30 eV)` is less than gold `(9.22 eV)`, yet `B` is a non-metal while gold is a metal.