Tag: study of orthoboric acid

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Multiple choice chemistry the p-block elements - group 13 study of orthoboric acid some important compounds of boron study of boron

Which one of the following statements about $H _3BO _3$ is not correct?

  1. It is a strong tribasic acid

  2. It is a prepared by acidifying an aqueous solution of borax
  3. It has a layer structure in which planar $BO _3$ units are joined by hydrogen bonds

  4. It does not act as proton donor as it acts as a Lewis acid by accepting hydroxyl ions
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

It is weak monoprotic acid and it does not act as proton donor but removes proton from water.

Multiple choice chemistry the p-block elements - group 13 study of orthoboric acid some important compounds of boron study of boron

$B _{2}Ca _{6}O _{11}+ Na _{2}CO _{3}\overset{\Delta }{\rightarrow}\left [ X \right ]+CaCO _{3}+NaBO _{2}$ (unbalanced equation)
Correct choice(s) for [X] is/are:

  1. structure of anion of crystalline [X] has one boron atom sp$^{3}$ hybridised and other three boron atoms sp$^{2}$
    hybridised

  2. X with NaOH (aq.) gives a compound which on reaction with hydrogen peroxide in alkaline medium yields
    a compound used as brightner in soaps
  3. hydrolysis of [X] with HCl or H$ _{2}$SO$ _{4}$ yields a compound which on reaction with HF gives fluoroboric acid

  4. [X] on heating with chromium salts in oxidising flame gives green coloured bead in cold
Reveal answer Fill a bubble to check yourself
B,C,D Correct answer
Explanation

Compound [X] is Na$ _{2}$B$ _{4}$O$ _{7}$
(A) two boron atoms are $sp^{2}$ while other two boron atoms are $sp^{3}$ hybridised.
(B) product is sodium peroxoborate which is used as brightner in soaps.
(C) $H _{3}BO _{3}$ is formed which with HF gives $HBF _{4}$.
(D) Green bead in oxidising as well as in reducing flame in cold.