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MolSynapse / Question bank / p-Block Elements: Groups 13 and 14 / Boron compounds: diborane, boric acid, borax, boron halides

NEET levelSingle correct optionDifficulty 1 of 3pb168

In the borax bead test, a copper(II) salt heated in the oxidising flame gives a bead that is blue (after cooling) because of formation of

A $Cu (BO X_{2}) X_{2}$
B $CuBO X_{2}$
Cmetallic copper
D $CuCl X_{2}$

Answer: A

Borax on heating gives

NaBO X_{2}

and

B X_{2} O X_{3}

.

B X_{2} O X_{3}

combines with

CuO

to give the blue cupric metaborate,

CuO + B X_{2} O X_{3} Cu (BO X_{2}) X_{2}

.

Practice p-Block Elements: Groups 13 and 14 More on Boron compounds: diborane, boric acid, borax, boron halides

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