Tag: p- block elements-ii

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

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

  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 $N(SiH _3) _3$
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

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

  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 $\displaystyle { NO } _{ 2 }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

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

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

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

  1. hydrogen bond

  2. ionic bond

  3. polar covalent bond

  4. pure covalent bond

  5. metallic bond
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

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

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

The correct order of stability is

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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:
$N _2>N _2^+>N _2^-$

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

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

  1. ${ NO } _{ 3 }^{ - }$
  2. ${ CO } _{ 3 }^{ - }$
  3. ${ BO } _{ 3 }^{ - }$
  4. ${ SO } _{ 3 }^{ - }$
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

Which of the following statements is correct ?

  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 ${\left( {{\text{C}}{{\text{H}} _{\text{3}}}} \right) _{\text{3}}}{\text{SiOH}}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In trisilylamine N(SiH3)3, the nitrogen uses its lone pair to form pπ-dπ back bonds with empty d-orbitals of silicon. This is similar to back bonding in trimethylamine N-oxide. Option B is incorrect (no count given), Option C's hybrid claim is questionable, and Option D is wrong - silanols are more acidic than alcohols.