Question

$ C{a_2}{B_6}{O_{11}} \to [X] + CaC{O_3} + NaB{O_2} $ (unbalanced equation)which of the following is/are correct choices(s) for $ [X] $
(A) The structure of anion of crystalline $ [X] $ has been boron atom $ s{p^3} $ hybridized and other three boron atoms $ s{p^3} $ hybridized.
(B) $ X $ with $ NaOH $ gives a compound which on reaction with hydrogen peroxide in alkaline medium yields a compound used as the brightener in soaps.
(C) Hydrolysis of $ [X] $ with $ HCl $ or $ {H_2}S{O_4} $ yields a compound which on reaction with $ HF $ gives fluoroboric acid.
(D) $ [X] $ on heating with chromium salts in oxidizing flame gives green colored beads.

Answer 1

Hint: The bead test is a traditional part of qualitative inorganic analysis to test for the presence of certain metals. The oldest one is the borax bead test or blister test. It was introduced by Berzelius in 1812. Since then other salts were used as fluxing agents, such as sodium carbonate or sodium fluoride.

Complete answer:
The compound $ X $ is borax $ (N{a_2}{B_4}{O_7}) $ . It is prepared by boiling finely powdered colemanite mineral $ (C{a_2}{B_6}{O_{11}}) $ with sodium carbonate solution.
 $ C{a_2}{B_6}{O_{11}} + 2N{a_2}C{O_3} \to 2CaC{O_3} + N{a_2}{B_4}{O_7} + 2NaB{O_2} $
The statements $ (B),(C) $ and $ (D) $ are correct. The statement $ (A) $ is incorrect.
 $ (A) $ The structure is anion of crystalline $ [X] $ has two boron atoms $ s{p^3} $ hybridized and other two boron atoms $ s{p^2} $ hybridized.
 $ (B) $ $ X $ with $ NaOH(aq) $ ,gives sodium metaborate $ NaB{O_2} $ which on reaction with hydrogen peroxide in alkaline medium yield hexahydrate sodium tetraaquaduperoxoborate(III)
 $ 2NaB{O_2} + 2{H_2}{O_2} + 6{H_2}O \to N{a_2}[{B_2}{({O_2})_2}{(OH)_4}].6{H_2}O $
 $ (C) $ Hydrolysis of $ [X] $ with $ HCl $ or $ {H_2}S{O_4} $ yields boric acid which in reaction with $ HF $ gives fluoroboric acid.
 $ N{a_2}{B_4}{O_7} + {H_2}S{O_4} \to N{a_2}S{O_4} + {H_2}{B_4}{O_7} $
 $ {H_2}{B_4}{O_7} + 5{H_2}O \to 4{H_3}B{O_3} $
 $ {H_3}B{O_3} + 4HF \to H[B{F_4}] + 3{H_2}O $
 $ (D) $ $ [X] $ on heating with chromium slats in oxidizing flame gives green colored beads.
 $ Cr{O_3} + 3{B_2}{O_3} \to 2Cr(B{O_2})3 $
This is a borax bead test.

Note:
A small loop is made at the end of a platinum or nichrome wire and heated in a Bunsen burner flame until red hot. A stick made of another inert substance such as a magnesia stick (MgO) may also be used. It is then dipped into powdered borax and held in the hottest part of the flame where it swells up as it loses its water of crystallization and then shrinks, forming a colourless, transparent glass-like bead.