Starting from boric acid prepare :
(a) Boric anhydride
(b) Boron trichloride
( c) Boron trifluride
(d) Metaboric acid
( e) Ethyl borate.

Explanation

(a) On strong heating, boric acid gives boric anhydride.
`2H_(3) BO_(3) overset("Red hot")rarr underset("Boric anhydride") (B_(2) O_(3)+ 3H_(2) O)`
(b) Boric acid is first converted to boric anhydride, `B_(2) O_(3)`. `B_(2) O_(3)` is then mixed with carbon and the mixture is heated in a current of chlorine when boron trichloride, `BCl_(3)` is formed.
`2H_(3) BO_(3) overset("Red hot")rarr B_(2) O_(3) + 3 H_(2) O`
`B_(2) O_(3) + 3C + 3Cl_(2) rarr 2BCl_(3) + 3CO`
( c) Boron triflurode, `BF_(3)`. is prepared by heating boric acid with `CaF_(2)` and `conc H_(2) SO_(4)`.
`2H_(3) BO_(3) + 3CaF_(2) + 3H_(2) SO_(4) rarr 2BF_(3) uarr + 3CaSO_(4) darr + 6H_(2) O`
(d) `H_(3) BO_(3)` when heated at `100^@ C`, decoposes to give metaboric acid.
`H_(3) BO_(3) overset(100^@ C)rarr underset("Metaboric acid") (HBO_(2))+H_(2) O`
( e) By heating boric acid with ethyl alcohol in the presence of `conc H_(2) SO_(4)`, ethyl borate is formed. (Conc `H_(2) SO_(4)` acts as dehydrating agent)
`H_(3) BO_(3) + 3C_(2) H_(5) OH overset(H_(2) SO_(4))rarr underset("Ethyl borate")(B(OC_(2) H_(5))_(3)) + 3H_(2) O`.