Question

$C{a}_2{B}_6{O}_{11}\stackrel{\Delta }{\to }\left[X\right]+CaC{O}_3+NaB{O}_2$ (unbalanced equation)
Correct choice(s) for [X] is /are:

• A. Structure of anion of crystalline [X] has one boron atom $s{p}^3$ hybridised and other three boron atoms $s{p}^2$ hybridised.
• B. X with NaOH (aq). gives a compound which one reaction with hydrogen peroxide in alkaline medium yields a compound used as brighter 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 oxidising flame gives green coloured bead in cold.

Answer 1

Answer: (B), (C), (D)

X with NaOH (aq). gives a compound which one reaction with hydrogen peroxide in alkaline medium yields a compound used as brighter in soaps.
Hydrolysis of [X] with HCl or $H_{2}S{O}_4$ yields a compound which on reaction with HF gives fluoroboric acid.
[X] on heating with chromium salts in oxidising flame gives green coloured bead in cold.

Compound [X] is $N{a}_2{B}_4{O}_7$.
(A) Two boron atoms are $s{p}^2$ while other two boron atoms are $s{p}^3$ hybridised.
(B) Product is sodium peroxoborate which is used as brightner in soaps.
(C) $H_{3}B{O}_3$ is formed which with HF gives $HB{F}_4$
(D) Green bead in oxidising as well as in reducing flame in cold.