Tag: study of boron

Questions Related to study of boron

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.

Identify the statement that is not correct as far as structure of diborane is concerned.

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

  1. There are two bridging hydrogen atoms in diborane

  2. Each boron atom forms four bonds in diborane

  3.  All B - H bonds in diborane are similar

  4. Diborane contains 3c-2$e^{-}$ bonds

Show answer
Correct Option: C

In diborane:

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

  1. 4 bridged hydrogen and two terminal hydrogen are present

  2. 2 bridged hydrogen and four terminal hydrogen are present

  3. 3 bridged hydrogen and three terminal hydrogen are present

  4. None of the above

Show answer
Correct Option: B
Explanation:

In diborane, there are 2 bridged $H$ atoms and 4 terminal $H$ atoms as shown in figure.

When an inorganic compound (X) having 3c-2e as well as 2c-2e bonds reacts with ammonia gas at a certain temperature and gives a compound(Y) iso-structural with benzene.Compound (X) with ammonia at a high temperature, produces a hard substance (Z).Then:

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

  1. X is $B _{2}H _{6}$

  2. Z is known as inorganic graphite

  3. Z having structure similar to graphite

  4. Z having structure similar to X

Show answer
Correct Option: A,B,C
Explanation:

X is $B _2H _6$ having 3c-2e as well as 2c-2e bonds. $B _2H _6$ reacts with $NH _3$ to form borazine or inorganic benzene. Z is $(BN) _x$ is called inorganic graphite and has similar structure to graphite. The whole reaction is shown in figure.

An example of three centred bond is:

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

  1. $BN$

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

  3. $NaBH _{4}$

  4. $B _{2}H _{6}$

Show answer
Correct Option: D

In the reaction, $2X+B _{2}H _{6}\rightarrow [BH _{2}(X) _{2}]^{+}BH _{4}^{-}$, the amine(s) X is (are) :

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

  1. $NH _{3}$

  2. $CH _{3}NH _{2}$

  3. $(CH _{3}) _2NH$

  4. $(CH _{3}) _{3}N$

Show answer
Correct Option: A,B,C
Explanation:

Smaller amines such as $NH _3$, $CH _3NH _2$ and $(CH _3) _2NH$ give unsymetrical cleavage of diborane according to following reaction
$2NH _3+B _{2}H _{6}\rightarrow [BH _{2}(NH _3) _{2}]^{+}BH _{4}^{-}$
Large amines such as $(CH _3) _3N$ give symmetrical cleavage of diborane according to following reaction
$B _2H _6 + 2N(CH _3) _3 \rightarrow 2(CH _3) _3N \rightarrow BH _3$

Select the incorrect statement 

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

  1. Diborane is $e^-$ deficient molecule

  2. Borazine is similar to benzene

  3. Baeyers's process is used to purify red Bauxite

  4. $BF _3$ is most acidic in boron trihalides

Show answer
Correct Option: D

Diborane $(B _2H _6)$ on combustion give 

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

  1. Boron

  2. Hydrogen

  3. $B _2O _3$

  4. $H _2B _4O _7$

Show answer
Correct Option: C
Explanation:

The combustion of diborane give $B _2O _3$

according to the reaction 
$B _2H _6(g) + 3O _2(g) \rightarrow B _2O _3(s) + 3H _2O()g$.