Tag: the p-block elements - group 13

Questions Related to the p-block elements - group 13

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

  1. there are two bridging hydrogen atoms in

    diborane

  2. each boron atom forms four bonds in diborane

  3. the hydrogen atoms are not in the same plane

    in diborane

  4. all B-H bonds in diborane are similar


Correct Option: D
Explanation:

There are 4 2c-2e B-H bonds and 2 3c-2e bonds in diborane.

In diborane, the Tau-bonds can be formed by the overlapping of orbitals :

  1. $sp^{3}-s-sp^{3}$

  2. $sp^{3}-sp^{3}$

  3. $sp^{2}-sp^{3}$

  4. $sp^{2}-s-sp^{2}$


Correct Option: A
Explanation:

In diborane, ${sp}^{3}$ hybrid orbital from each boron overlaps with 1$s$ orbital of $H$ atom to form 3 center-2 electron (3c-2e) bond.

$B _{2}H _{6}$ undergoes substitution reaction with:

  1. $Br _{2}$ at $100^{o}C$

  2. $HCl$ $/$anhydrous $AlCl _{3}$

  3. both A and B

  4. $Cl _{2}$ at $100^{o}C$


Correct Option: C
Explanation:

$B _2H _6 + HCl \rightarrow B _2H _5Cl + H _2$
This reaction takes place in the presence of anhydrous $AlCl _3$.
$B _2H _6 + Br _2 \rightarrow B _2H _5Br + HBr$
This is a slow reaction taking place at $100^oC$.
$B _2H _6 + 6Cl _2 \rightarrow 2BCl _3 + 6HCl$
This is a vigorous reaction taking place at $25^oC$. Diborane does not react with $Cl _2$ at ${100}^{o}C$. This reaction is not reported.

With which of the following diborane does not produce hydrogen?

  1. NaOH

  2. $Cl _{2}$

  3. $H _{2}O$

  4. HCl


Correct Option: B
Explanation:

$B _{2} H _{6} + 6Cl _{2} \rightarrow 2BCl _{3} + 6HCl $ 

Thus, with chlorine diborane does not form hydrogen.

The non planar molecule among the following is:

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

  2. $C _{2}H _{4}$

  3. $C _{6}H _{6}$

  4. $BCl _{3}$


Correct Option: A
Explanation:

diborane has non-planar structure. It has 2 hydrogen atoms which are present above and below the plane of the boron and hydrogen bond. 

In the case of small cuts, bleeding is stopped by applying potash alum, hence alum acts as:

  1. germicide

  2. disinfectant

  3. fungicide

  4. coagulating Agent


Correct Option: D
Explanation:

Clotting of blood is called coagulation and a substance promoting this is called coagulating agent.

All the $Al-Cl$ bonds in $Al _2Cl _6$ are equivalent.
  1. True

  2. False


Correct Option: B
Explanation:

The given statement is False.
All the  $\displaystyle Al-Cl$ bonds in $\displaystyle Al _2Cl _6$ are not equivalent.
Two types of bonds are present in $\displaystyle Al _2Cl _6$, terminal $\displaystyle Al-Cl$ bonds that are normal $\displaystyle 2c-2e$ bonds and $\displaystyle Al-Cl-Al$ bridges that are $\displaystyle 3c-4e$ bonds.

Which one of the following does not exist in the free form ?

  1. $BF _{3}$

  2. $BCl _{3}$

  3. $BBr _{3}$

  4. $BH _{3}$


Correct Option: D

From $B _2H _6$, all the following can be prepared except :

  1. $B _2O _3$

  2. $H _3BO _3$

  3. $B _2(CH _3) _6$

  4. $NaBH _4$


Correct Option: C
Explanation:
$B _2H _6+3O _2\rightarrow B _2O _3+3H _2O+Heat$

$B _2H _6+6H _2O\rightarrow H _3BO _3+6H _2$

$2NaH+B _2H _6\rightarrow etherNaBH _4$

From $B _2H _6$, all can be prepared except $B _2(CH _3) _6$

Hence option $C$ is correct.

The hydrides of boron are called :

  1. Boron hydrogen compounds

  2. Hydrogen borides

  3. Boranes

  4. Hydroboric acids


Correct Option: C