Tag: study of diborane

Questions Related to study of diborane

Boron halides behave as Lewis acids because of their ________ nature.

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

  1. proton donor

  2. covalent

  3. electron deficient

  4. ionising

Show answer
Correct Option: C
Explanation:

According to Lewis, the compound which can accept a lone pair of electron, are called acids.
Boron halides, being electron deficient compounds, can accept a lone pair of electrons, so termed as Lewis acid.

Diborane combines with ammonia at ${120}^{o}C$ to give:

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

  1. ${B} _{2}{H} _{6}.{NH} _{3}$

  2. ${B} _{2}{H} _{6}.2{NH} _{3}$

  3. ${B} _{2}{H} _{6}.3{NH} _{3}$

  4. none of the above

Show answer
Correct Option: B
Explanation:

Diborane combines with ammonia to form a borazine.

${ B } _{ 2 }{ H } _{ 6 }+2N{ H } _{ 3 }\rightarrow { B } _{ 2 }{ H } _{ 6 }.2N{ H } _{ 3 }$
The reaction proceeds further to form inorganic benzene.
$2{ B } _{ 2 }{ H } _{ 6 }.2N{ H } _{ 3 }\rightarrow 2{ B } _{ 3 }{ N } _{ 3 }{ H } _{ 6 }+12{ H } _{ 2 }$
Here, ${ B } _{ 3 }N _{ 3 }{ H } _{ 6 }$ is inorganic benzene.

Number of terminal hydrogen atoms present in diborane?

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

  1. 2

  2. 4

  3. 6

  4. 8

Show answer
Correct Option: B
Explanation:

Diborane is an electron deficient molecule. The two boron atoms and the four terminal hydrogen atoms of the molecule are all in the same plane. These four terminal B -H bonds are regular 2-centered- 2 electron bonds. The bridging hydrogen atoms lie above and below this plane.

Hence option B is correct answer.

Borazine is sometimes called inorganic benzene. Which of the following reactions is expected to give this compound?

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

  1. $B _{2}H _{6}+NH _{3} \xrightarrow [ excess\ { NH } _{ 3 } ]{ low\ tem } $

  2. $B _{2}H _{6}+NH _{3} \xrightarrow [ excess\ { NH } _{ 3 } ]{ high\ tem } $

  3. $B _{2}H _{6}+NH _{3} \xrightarrow [ ratio\ 2\ { NH } _{ 3 }:1{ B } _{ 2 }{ H } _{ 6 } ]{ high\ tem } $

  4. $All\ of\ these$

Show answer
Correct Option: C
Explanation:
Borazine is an inorganic compound with the chemical formula ${ (BH } _{ 3 }{ )(NH } _{ 3 })$ In this cyclic compound, the three BH units and three NH units alternate. The compound is isoelectronic and isostructural with benzene. Like benzene, borazine is a colourless liquid. For this reason, borazine is sometimes referred to as "inorganic benzene"

Borazine is synthesized from diborane and ammonia in a 1:2 ratio at 250–300 °C with a conversion of 50%.

$3B _2H _6 + 6NH _3 \rightarrow 2B _3H _6N _3 + 12H _2$

$BCl _3+LiAlH _4\rightarrow A+LiCl+AlCl _3$
$A+H _2O\rightarrow B+H _2$
$B\rightarrow C$.
in this reaction sequence A, B, and C compounds respectively are?

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

  1. $B _2H _6,B _2O _3,B$

  2. $B _2H _6,H _3BO _3,B _2O _3$

  3. $B _2H _6,H _3BO _3,B$

  4. $HBF _4,H _3BO _3,B _2O _3$

Show answer
Correct Option: B
Explanation:

The reactions given are,

$LiAlH _4 + BCl _3 \rightarrow B _2H _6 + LiCl + AlCl _3$
Hence A is $B _2H _6$

Now, second reaction is,
$B _2H _6 +H _2O \rightarrow H _3BO _3 +H _2$
Hence B is $H _3BO _3$

On heating B i.e. $H _3BO _3$ we get $B _2O _3$

$B _2H _6 + NH _3 \rightarrow$ Addition compound $(X)$
$(X) \overset{450K}{\rightarrow} Y + Z(g)$
In the above sequence $Y$ and $Z$ are respectively:

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

  1. borazine, $H _2O$

  2. boron, $H _2$

  3. boron nitride, $H _2$

  4. borazine and hydrogen

Show answer
Correct Option: D
Explanation:

$B _2H _6+2NH _3 \longrightarrow \underset {(X)}{B _2H _62NH _3}$

$3B _2H _62NH _3\xrightarrow[]{450K}\underset {(Y)}{2B _3N _3H _6}+\underset {(Z)}{3H _2}$
$(Y)$ & $(Z)$ are borazine and $H _2$ respectively.

Diborane belongs to the :

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

  1. ${ B } _{ n }{ H } _{ n+6 }$ series

  2. ${ B } _{ n }{ H } _{ n+1 }$ series

  3. ${ B } _{ n }{ H } _{ n+4 }$ series

  4. ${ B } _{ n }{ H } _{ n+8 }$ series

Show answer
Correct Option: C
Explanation:

The chemical formula for diborane is $B _2H _6$ which resembles general formula $B _n{H} _{n+4}$.

The product obtained when one mole of diborane reacts with two mole of $NH _3 $ at high temperature ?

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

  1. $B _2H _6.2NH _3 $

  2. $B _3N _3H _6 $

  3. $(BN) _x $

  4. $ [BH _2 (NH _3) _2]^ + BH _4^- $

Show answer
Correct Option: B
Explanation:
Diborane react with ammonia
$3B _2H _6 + 6NH _3 → 2B _3N _3H _6 + 12H _2$
So the ratio of combination of $B _2H _6$ and $NH _3$ is $1:2$
Hence option B is correct answer.

On hydrolysis, diborane produces:

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

  1. ${ H } _{ 3 }BO _{ 2 }+H _{ 2 }{ O } _{ 2 }$

  2. ${ H } _{ 3 }BO _{ 3 }+H _{ 2 }$

  3. $B _{ 2 }O _{ 3 }+{ O } _{ 2 }$

  4. $H _{ 3 }BO _{ 3 }+{ H } _{ 2 }{ O } _{ 2 }$

Show answer
Correct Option: B
Explanation:
Diborane react with water to give following products,
$B _2H _6 + 6H _2O → 2H _3BO _3 + 6H _2$
Hence option $B$ is correct answer.

Diborane is:

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

  1. electron-sufficient

  2. electron-deficient

  3. electron-donor

  4. none

Show answer
Correct Option: B
Explanation:

Diborane is electron-deficient i.e, there are not enough valence electrons to form the expected number of covalent bonds. For example, in diborane, there are only 12 electrons, three from each boron atoms and six from hydrogen, while ethane possesses 14 such electrons.