Complete the following :

Explanation

(a) Since the compound of bororn is obtained, so compound `(X)` is `BCl_(3)`. Reactions are :

(b) Since the end product is boric acid `(H_(3) BO_(3))` hence the element `E`, must be boron `(B)`.
.
Reactions are :
(i) `underset((E))(4B)+ 3O_(2) rarr underset((F))(2B_(2) O_(3))`
(ii) `underset((F))(B_(2)O_(3)) + N_(2(g))rarr underset((H))(2BN) + 3//2 O_(2(g))`
(iii) `2BN + 3H_(2)O rarr B_(2) O_(3) + 2NH_(3)`
`B_(2)O_(3) + H_(2) O rarr HBO_(2)`
`HBO_(2) + H_(2) O rarr H_(3)BO_(3)(Boric acid)`.