Tag: the p-block elements - group 13

Questions Related to the p-block elements - group 13

Which of the following is correct statement?

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

  1. Boric acid is a protonic acid

  2. Beryllium exhibits coordination number of six

  3. Chlorides of both beryllium and aluminium have bridged chloride structures in solid phase

  4. ${B} _{2}{H} _{8}.2{NH} _{3}$ is known as borazone

Show answer
Correct Option: C

$H _{3}BO _{3}$ is a:

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

  1. monobasic acid and weak Lewis acid

  2. monobasic acid and weak Bronsted acid

  3. monobasic acid and strong Lewis acid

  4. tribasic acid and weak Bronsted acid

Show answer
Correct Option: A
Explanation:

It is a monobasic acid and a weak lewis acid. It accepts an electron pair from $OH^{-}$.


$B(OH) _{3} + 2H _{2} O \rightleftharpoons [B(OH) _{4} ]^{-} +H _{3} O^{+} $

Option A is correct.

Boric acid is the trival name for ?

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

  1. orthoboric acid

  2. metaboric acid

  3. pyroboric acid

  4. None of these

Show answer
Correct Option: A
Explanation:

Answer:- (A) Orthoboric acid

Boric acid is a weak, mono-basic Lewis acid of boron, which is often used as an antiseptic, insecticide, flame retardant, neutron absorber, or precursor to other chemical compounds and also known as orthoboric acid (trival name).
The chemical formula of boric acid is $H _3BO _3 \; or \; B{(OH)} _3$.

Boric acid on heating at $100^oC$ gives:

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

  1. $B _2O _3$

  2. $H _2B _4O _7$

  3. $HBO _2$

  4. $H _2BO _3$

Show answer
Correct Option: C
Explanation:
  • Orthoboric acid, $H _3BO _3$ is a white crystalline solid, with soapy touch. It is sparingly soluble in water but highly soluble in hot water.
  • On heating, orthoboric acid above 370K forms metaboric acid, $HBO _2$ which on further heating yields boric oxide, $B _2O _3.$
  • Hence option C is correct answer.

$\displaystyle B(OH) _{3}+NaOH\rightleftharpoons NaBO _{2}+Na[B(OH) _{4}]+H _{2}O$ 

How can this reaction is made to proceed in forward direction?

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

  1. Addition of cis 1,2 diol

  2. Addition of borax

  3. Addition of trans 1,2 diol

  4. Addition of $Na _{2}HPO _{4}$

Show answer
Correct Option: A
Explanation:

cis -1,2 diol is added to make the recation proceed in the forward direction.

$H _{3}BO _{3}\xrightarrow{T _{1}}X \xrightarrow{T _{2}} Y\xrightarrow{red hot} B _{2}O _{3}$ if $T _{1}<T _{2}$then X and Y respectively are :

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

  1. X=Metaboric acid and Y= Tetraboric acid

  2. X=Tetraboric acid and Y= Metaboric acid

  3. X=Borax and Y= Metaboric acid

  4. X=Tetraboric acid and Y= Borax

Show answer
Correct Option: A
Explanation:

$H _{3}BO _{3}\xrightarrow{100^oC}HBO _2 \xrightarrow{160^oC} H _2B _4O _7\xrightarrow{red hot} B _{2}O _{3}$
X is $HBO _2$ which is metaboric acid and Y is $H _2B _4O _7$ which is tetraboric acid.

Which of the following is correct statement?

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

  1. Boric acid is a protonic acid

  2. Beryllium exhibits coordination number of six

  3. Chlorides of both beryllium and aluminium have bridged chloride structures in solid phase

  4. ${B} _{2}{H} _{6}.2{NH} _{3}$ is known as borazone

Show answer
Correct Option: D

Which one of the following is the correct statement?

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

  1. Boric acid is a protonic avid.

  2. Both ${\text{T}}{{\text{l}}^{{\text{3 + }}}}{\text{and}}\;{\text{A}}{{\text{l}}^{{\text{3 + }}}}$ ions act oxidsing agent in aqueous solution.

  3. Hydrogen bonding in gives it a layered structure

  4. imparts bile colour to the burner flame.

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Correct Option: D

The equilibrium constant for the reaction: $ H _3BO _3 + glycerin \rightleftharpoons (H _3BO _3 + glycerin complex ) $ is 0.90. How much glycerin should be added to I L of $ 0.10 M-H _3BO _3 $ solution, so that 60% of the $ H _3BO _3 $ is converted to boric acid glycerin complex?

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

  1. Infinite

  2. 1.73 M

  3. 0.10 M

  4. 2.27 M

Show answer
Correct Option: B

$H _3BO _3$ is :

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

  1. monobasic and weak Lewis acid.

  2. monobasic and weak Bronsted acid.

  3. monobasic acid and strong Lewis acid.

  4. tribasic acid and weak Bronsted acid.

Show answer
Correct Option: A
Explanation:

$\mathrm{H} _{3}\mathrm{B}\mathrm{O} _{3}(\mathrm{C})$ (orthoboric acid) is a weak lewis acid.

$\mathrm{H} _{3}\mathrm{B}\mathrm{O} _{3}+\mathrm{H} _{2}\mathrm{O} _{-}^{-}\mathrm{E}(\mathrm{O}\mathrm{H}) _{4}^{-}+\mathrm{H}^{\oplus}$

So as it releases one $H^{+}$ so its Monobasic and weak Lewis acid

Hence option A is correct.