Q. Show the Reactions of Boric Oxide?
Boric oxide, B203, is the principal oxide of boron. It is also known as boron trioxide, boron sesquioxide and boric anhydride. It is prepared by burning boron in oxygen or by heating boric acid to red heat:
2B + 302-------------------------> p B203
2H3BO3---------------------------> B203 + 3H20
Boric oxide is a white hygroscopic solid. It is acidic in nature and dissolves in water to form boric acid:
B2O3 + 3H2O---------------------------------> 2H3BO3
When fused with metal salts, it forms, Meta borates known as borate glasses. Meta borates of coloured cations have characteristic colours. This forms the basis of the borax-bead test in qualitative inorganic analysis, e.g.:
COO + B2O3------------------------------------->CO (BO2)2, deep blue
CuS04 + B203 ---------------------------------->CU (BO2)2, blue
Cr2 (S04)3 + B203-------------------------------> 2Cr (BO2)3, green
The bond energy of the B-0 single bond is very high (523 kJ mol-1). Therefore, unlike carbon and nitrogen, boron does not form stable BO double bonds to oxygen. Instead of forming small volatile covalent molecule, B203 (g) and small anion, B03-33 it forms polymers having -B-0-B-0-B-0- chains. Thus, boric oxide is a polymeric solid.