Tag: p- block elements-ii

Questions Related to p- block elements-ii

Which of the following is correct statement regarding $N(CH _3) _3$ and $N(SiH _3) _3$?

chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

  1. $N(SiH _3) _3$ is planar and more basic than $N(CH _3) _3$

  2. $N(SiH _3) _3$ is planar and less basic than $N(CH _3) _3$

  3. $N(CH _3) _3$ is planar and more basic than $N(SiH _3) _3$

  4. $N(CH _3) _3$ is pyramidal and less basic than $N(SiH _3) _3$

Show answer
Correct Option: B
Explanation:

$N(SiH _3) _3$ is planar due to back bonding and $N(CH _3) _3$ more basic due to presence of lone pair electrons.

The bond energy of $\mathrm{N}\equiv \mathrm{N}$ per mole is:

chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

  1. 180 kcal

  2. 225 kcal

  3. 350 kcal

  4. 120 kcal

Show answer
Correct Option: B
Explanation:

The bond energy of $N _2$ per mole is 225 kcal or 945 KJ/ mol


Hence, the correct option is $\text{B}$

Which of the following pairs is obtained on heating ammonium dichromate?

chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

  1. $\displaystyle { N } _{ 2 }$ and $\displaystyle { H } _{ 2 }O$

  2. $\displaystyle { N } _{ 2 }O$ and $\displaystyle { H } _{ 2 }O$

  3. $\displaystyle { NO } _{ 2 }$ and $\displaystyle { H } _{ 2 }O$

  4. $\displaystyle NO$ and $\displaystyle { NO } _{ 2 }$

Show answer
Correct Option: A
Explanation:

Ammonium dichromate on heating gives nitrogen, chromic oxide and water.
$\displaystyle { \left( { NH } _{ 4 } \right)  } _{ 2 }{ Cr } _{ 2 }{ O } _{ 7 }\underrightarrow { \Delta  } { N } _{ 2 }+{ Cr } _{ 2 }{ O } _{ 3 }+4{ H } _{ 2 }O$

The type of bond between the atoms in a nitrogen molecule is :

chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

  1. hydrogen bond

  2. ionic bond

  3. polar covalent bond

  4. pure covalent bond

  5. metallic bond

Show answer
Correct Option: D
Explanation:

The atomic number of nitrogen is 7.

Its electronic configuration is $[He]{ 2s }^{ 2 }{ 2p }^{ 5 }$
To complete its octet it needs 3 electrons.
As the bonding is between 2 nitrogen atoms each of the atom will share 3 electrons with other to complete their octet.
Sharing of electrons results in covalent bonding.
Hence, they form pure covalent bonds.

Nitrogen form $N _2$, but phosphorous form $P _2$, it's at a time convert in $P _4$, reason is : -

chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

  1. Triple bond present between phosphorous atom

  2. $p _\pi p _\pi$bonding is weak

  3. $p _\pi p _\pi$bonding is strong

  4. Multiple bond form easilly

Show answer
Correct Option: B
Explanation:

Phosphorus is unable to form $p\pi-p\pi$ bonds due to larger atomic size. So, $P$ atom is linked with $P$ atoms using $3$ sigma bonds. On the other hand, Nitrogen forms $1-\sigma$ and $2-\pi$ bonds i.e.,  triple bonds and exists as diatomic molecules.

Nitrogen is liberated by the thermal decomposition of only :

chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

  1. $NH _4NO _2$

  2. $NaN _3$

  3. $(NH _4) _2Cr _2O _7$

  4. All of these

Show answer
Correct Option: D
Explanation:

Nitrogen is liberated by the thermal decomposition of ammonium nitrite $(NH _4NO _2), NaN _3, (NH _4) _2Cr _2O _7$

-1/3 oxidation state of nitrogen will be obtained in case of ________.

chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

  1. hydroxylamine

  2. oxime

  3. hydrazoic acid

  4. none of these

Show answer
Correct Option: C
Explanation:

nitrogen show oxidation state of -1\3 in hydrazoic acid 

$H-N={ N }^{ + }={N:}^{ - }$

The correct order of stability is

chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

  1. ${ N } _{ 2 }>{ N } _{ 2 }^{ + }>{ N } _{ 2 }^{ - }$

  2. ${ N } _{ 2 }>{ N }^{ - } _{ 2 }>{ N } _{ 2 }^{ + }$

  3. ${ N } _{ 2 }^{ + }>{ N }^{ - } _{ 2 }>{ N } _{ 2 }$

  4. None of these

Show answer
Correct Option: A
Explanation:

Bond order for $N _2=3$

Bond order for $N _2^+=2.5$
Bond order for $N _2^-=2$
Bond order $\propto$ Stability of molecule.
Therefore, the correct order of stability is:
$N _2>N _2^+>N _2^-$

Which of the following has $p\pi -d\pi $ bonding?

chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

  1. ${ NO } _{ 3 }^{ - }$

  2. ${ CO } _{ 3 }^{ - }$

  3. ${ BO } _{ 3 }^{ - }$

  4. ${ SO } _{ 3 }^{ - }$

Show answer
Correct Option: D
Explanation:

$p\pi-d\pi$ bonding includes d-orbitals,if you observe the options only S belongs to $3^{rd}$ period and has d-orbitals(though unoccupied in ground state).

Other options $C$ and $N$ belongs to $2^{nd}$ period while B belongs to $1^{st}$ period and doesn't have d-orbitals.

Which of the following statements is correct ?

chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

  1. In trisilylamine $p\pi - d\pi $ back bonding takes place.

  2. These are two $p\pi - d\pi $ bonds in molecule.

  3. Fraction of s-character in hybride around the central atom in molecule is 0.5

  4. ${\left( {{\text{C}}{{\text{H}} _{\text{3}}}} \right) _{\text{3}}}{\text{COH}}$ is more acidic than ${\left( {{\text{C}}{{\text{H}} _{\text{3}}}} \right) _{\text{3}}}{\text{SiOH}}$

Show answer
Correct Option: A