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

The single $X-X$ bond made by $N$ is weaker than that of $P$ because:

  1. of repulsion between nitrogen nucleus due to smaller size of nitrogen atom

  2. of repulsion between non-bonded electrons due to smaller size of nitrogen atom

  3. of higher bond enthalpy of nitrogen

  4. all of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The single $N-N$ bonds formed is weaker than single $P-P$ bonds because of lone pair repulsion on small nitrogen molecule.

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

Which of the following does not contain nitrogen?

  1. Proteins in plants and animals

  2. Members of apatite family

  3. Indian saltpetre

  4. Chile saltpetre
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite and chlorapatite, with high concentrations of $OH^{-},F{-},Cl{-}$ respectively, in the crystal. Proteins in plants and animals have nitrogen. Chile saltpetre and Indian saltpetre are $NaNO _3$ and $KNO _3$ respectively.

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

Which of the following gives purest form of nitrogen?

  1. Thermal decomposition of ammonium nitrate

  2. Treating aqueous solution of ammonium chloride with sodium nitrite

  3. Thermal decomposition of sodium or barium azide

  4. Liquefaction and fractional distillation of air
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$2NaN _3 \rightarrow 2Na +3N _2$ 

Pure nitrogen can be obtained from thermal decomposition of sodium or barium azide.

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

Nitrogen and phosphorus are both in Group 15 of the Periodic Table. Phosphorus forms a chloride with the formula $P{Cl} _{5}$ but nitrogen does not form $N{Cl} _{5}$.
Which statements help to explain this?
1. Nitrogen's outer shell cannot contain more than eight electrons.
2. Nitrogen cannot have an oxidation state of $+5$
3. Nitrogen is less electronegative than phosphorus.

  1. 1, 2 and 3 are correct

  2. 1 and 2 only are correct

  3. 2 and 3 only are correct

  4. 1 only is correct
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Only highly electrnegative elements can make nitrogen exhibit +5 oxidation state


We know that, on going from top to bottom in a group, non- metalllic character decreases. The non- metallic character of any element is characterized by its tendency to lose electron i.e electronegativity.
Hence, electronegativity decreases on going from top to bottom in a group.
Therefore, Nitrogen is more electronegative than Phosphorus.

Also, Nitrogen is smaller in size as compared to Phosphorus. Due to its small size, the net electron charge increases. Hence, its nucleus exerts greater force on the electrons.
Thetefore, its tendency to gain electron is more as compared to that of Phosphorus.
That is the reason why, Nitrogen is more electronegative element than Phosphorus.


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

Select the correct statement for brown ring test.

  1. Nitrates are converted to $NO$
  2. $NO$ forms complex with $Fe$
  3. $Fe^{2+}$ acts as reducing agent here.

  4. Brown colour is due to the complex formation.
Reveal answer Fill a bubble to check yourself
A,B,C,D Correct answer
Explanation
$ 2HNO _3+ 3H _2SO _4 + 6FeSO _4 \rightarrow 3Fe _2(SO _4) _3 + 2NO + 4H _2O $ $[Fe(H _2O) _6]SO _4+NO \rightarrow [Fe(H _2O) _5(NO)]SO _4+H _2O$ Nitrates are converted into nitric oxide. $NO$ forms complex with $Fe$. $Fe^{2+}$ acts as reducing agent. $[Fe(H _2O) _5(NO)]SO _4$ is brown coloured complex formed.
Multiple choice chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

Which of the following do have $p _{\pi}$ - $d _{\pi}$ bonding?

  1. $NO^- _3$
  2. $SO^{-2} _3$
  3. $BO^{-3} _3$
  4. $CO^{-2} _3$
Reveal answer Fill a bubble to check yourself
B 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

Single $N-N$ bond is weaker than the single $P-P$ bond. This is because of:

  1. larger $N-N$ bond length in comparison to $P-P$ bond length
  2. high interelectronic repulsion of the non-bonding electrons, owing to the small $N-N$ bond length in comparison to that in $P-P$ single bond
  3. higher electronegativity of $N$ in comparison to $P$
  4. smaller atomic size of $N$ as compared to that of $P$
Reveal answer Fill a bubble to check yourself
B,D Correct answer
Explanation

$N-N$ single bond is weaker than $P-P$ bond due to smaller size of $N$ as compared to $P$. Smaller size of $N$ leads to smaller $N-N$ bond length. As a result, the lone pair of electrons on the both the $N$ atoms repel each other leading to unstability or weakening of $N-N$ bond. Because of larger size of $P$ atom, $P-P$ bond length is more and lone pair-lone pair repulsion between $P$ atoms is less which makes the $P-P$ bond stronger than $N-N$ bond.