Tag: anomalous properties of nitrogen

Questions Related to anomalous properties of nitrogen

Which of the following statements is wrong?

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

  1. Single N-N bond is stronger than the single P-P bond.

  2. $PH _{3}$ can act as a ligand in the formation of coordination compound with transition elements.

  3. $NO _{2}$ is paramagnetic in nature.

  4. Covalency of nitrogen in $N _{2}O _{5}$ is four.

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Correct Option: A
Explanation:

N-N sigma bond (single bod)  is weaker than P-P sigma bond (single bond) due to the small bond length between the nitrogen atoms. The lone pair of electrons of both the atoms nitrogen  repel each other making the single bon between $N-N$  weaker than P-P sigma bond.In $P-P$  bond the repulsion between sigma bond and lone pair electrons is less as the size of phosphorous is large.

So statement A is wrong.

Hence option A is correct.

Nitrogen forms stable $N _{2}$ molecule but phosphorus is converted to $P _{4}$ from $P _{2}$ because:

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

  1. p$\pi$-p$\pi$ bonding is strong in phosphorus

  2. p$\pi$-p$\pi$ bonding is weak in phosphorus

  3. triple bond is present in phosphorus

  4. single $P - P$ bond is weaker than $N -N$ bond

Show answer
Correct Option: B
Explanation:

$P$ has empty $d$ orbital, that can be filled by an additional electron. And since its size is bigger it is least likely to handle triple bond, as size increases $\pi$ overlapping decreases. 

Which of the following mlecular $P\pi -P\pi $ bond?

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

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

  2. CO

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

  4. ${ NO } _{ 4 }^{ -2 }$

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Correct Option: B

Which of the following  molecules is having $2p\pi -3d\pi $ bond?

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

  1. ${ SO } _{ 3 }$

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

  3. ${ SO } _{ 2- }^{ 4 }$

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

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Correct Option: B

Correct order of nucleophilicity?

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

  1. $CH _3O^- > CH _3^+ > NH _2^- > CH _3COO^-$

  2. $CH _3^+ > NH _2^- > CH _3O^- > CH _3COO^-$

  3. $NH _2^- > CH _3^+ >CH _3O^- > CH _3COO^-$

  4. $CH _3^+ > CH _3O^- > NH _2^- > CH _3COO^-$

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Correct Option: B

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 $N(SiH _3) _3$

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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.