How is boron obtained from borax ? Give the chemical reactions involved. Draw the structure of `B_(2)H_(6)` and give its reaction with `HCl`.

Explanation

The finely ground borax is heated with concentrated hydrrochloric acid or concentrated sulphuric acid when sparingly soluble orthoboric acid separates out.
`Na_(2)B_(4) O_(7) + 2HCl to 2NaCl + H_(2)B_(4)O_(7)`
`Na_(2)B_(4)O_(7) + H_(2)SO_(4) to Na_(2)SO_(4) + H_(2)B_(4)O_(7)`
`H_(2)B_(4)O_(7) + 5H_(2)O to 4H_(3)BO_(3)`
Orthoboric acid is strongly heated to get `B_(2)O_(3)`.
`2H_(3)BO_(3) to B_(2)O_(3) + 3H_(2)O`
The reduction of boric anhydride `(B_(2)O_(3))` can be done with sodium, potassium or magnesium.
`B_(2)O_(3) + 6K to 2B + 3K_(2)O`
`B_(2)O_(3) + 3Mg to 2B + 3MgO`
Boron is obtained these days by the electrolysis of a fused mixture containing boric anhydride magnesium oxide and magnesium fluoride. The electrolysis is done in carbon crucible which acts as the anode and iron rod is used as the cathode. The magnesium discharge at the cathode reduces `B_(2)O_(3)` to boron.
The structure of diborane is as follows :
`B_(2)H_(6)+HCl to underset("Chlorodiborane")(B_(2)H_(5)Cl)+ H_(2)`.