Tag: study of boron

Quizzes (0) Questions (137)

Questions Related to study of boron

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

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

  1. $B _2H _6.2NH _3 $
  2. $B _3N _3H _6 $
  3. $(BN) _x $
  4. $ [BH _2 (NH _3) _2]^ + BH _4^- $
Reveal answer Fill a bubble to check yourself
B Correct answer
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.
Multiple choice chemistry the p-block elements - group 13 study of diborane some important compounds of boron study of boron

On hydrolysis, diborane produces:

  1. ${ H } _{ 3 }BO _{ 2 }+H _{ 2 }{ O } _{ 2 }$
  2. ${ H } _{ 3 }BO _{ 3 }+H _{ 2 }$
  3. $B _{ 2 }O _{ 3 }+{ O } _{ 2 }$
  4. $H _{ 3 }BO _{ 3 }+{ H } _{ 2 }{ O } _{ 2 }$
Reveal answer Fill a bubble to check yourself
B Correct answer
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.
Multiple choice chemistry the p-block elements - group 13 study of diborane some important compounds of boron study of boron

Diborane is:

  1. electron-sufficient

  2. electron-deficient

  3. electron-donor

  4. none
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

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

  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
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In diborane, there are two types of B-H bonds: terminal and bridging. The terminal bonds are standard 2c-2e bonds, while the bridging bonds are 3c-2e bonds. Therefore, they are not all similar.

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

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:

  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
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
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.

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

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

  1. $NH _{3}$
  2. $CH _{3}NH _{2}$
  3. $(CH _{3}) _2NH$
  4. $(CH _{3}) _{3}N$
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
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
$B _2H _6 + 2N(CH _3) _3 \rightarrow 2(CH _3) _3N \rightarrow BH _3$

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

Select the incorrect statement 

  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
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

BF3 is actually the least acidic of the boron trihalides because of strong p-pi back-bonding from the fluorine atoms to the boron atom, which reduces the electron deficiency of the boron center.