P- Block Elements ( Group 14)

REASONING QUESTIONS OF P-BLOCK ELEMENTS CLASS-XII Q1) Nitrogen exists as a diatomic molecule and Phosphorous as P4 .Why? OR Nitrogen forms a larger number of oxides than phosphorous. Explain. OR Oxygen exists as a diatomic molecule and Sulphur as S8 .Why?

Ans) As nitrogen has a tendency to form pπ-pπ multiple bond due to small size and high electronegativity while Phosphorous can’t form due to large size. 

Q2) Nitrogen is inert(less reactive) at room temperature. Why?

Ans) Because it has triple bond, so its bond dissociation enthalpy is very high.

Q3)Why does nitrogen show catenation property less than phosphorous? OR Sulphur exhibits tendency for catenation but oxygen doesn’t. Why?

Ans) As single N-N bond is weaker than the single P-P bond because of high interelectronic repulsion of the non-bonding electrons, due to small bond length in N2. Q4) Q4) N2is a gas while P4 is a solid at room temperature. Why? OR Explain why Oxygen is a gas while sulphur is a solid.

Ans) N2 molecules are attracted to each other through weak vanderwaal forces which can be easily overcome by the energy available at room temperature while 4 P (8 S) atoms are linked through covalent bonds which can’t be broken at room temperature.

Q5) The stability of +5 oxidation state decreases on moving down the group. Why? OR Stability of higher oxidation state decreases on moving down the group. Explain. OR Bi is a strong oxidizing agent in pentavalent state. OR The +5 oxidation state of Bi is less stable than its +3 state. Why OR SbF5 is much more stable than BiF5. Why? Ans) Due to inert pair effect, the ns electrons can’t participate in the bond formation.

Q6) Nitrogen shows maximum covalence of 4. Why? OR Though nitrogen exhibits +5 oxidation state, it doesn’t form pentahalides.Why? OR Why phosphorous form PF5 while nitrogen does not form NF5.OR Oxygen shows maximum covalence of 4. Why? OR ClF3 exists but FCl3 doesn’t. Why? OR Why does oxygen not show an oxidation state of +4 and +6 like sulphur? 

Ans) Due to absence of d orbitals in nitrogen.(oxygen or fluorine)

Q7) Why does nitrogen show anomalous behavior? OR Why does oxygen show anomalous behavior?

Ans) Because of smaller size, absence of d-orbitals, high electronegativity and high ionization enthalpy.

Q8) NH3 is liquid at room temperature while PH3 is a gas. Why? OR NH3 has higher boiling point than PH3. Why? H2O is liquid at room temperature while H2S is a gas. Why?

Ans) Because NH3 molecules are associated to each other through intermolecular hydrogen bonds while PH3 molecules can’t form hydrogen bonds.

Q9) PH3 is a weaker base than NH3. Why? OR NH3 is basic while BiH3 is only feebly basic. Why?

Ans) P is having larger size and less electronegativity than N, therefore tendency to donate the lone pair is less in PH3.

Q10) Why is NH3 a good complexing agent? OR Why does NH3 act as a Lewis base? OR NH3 act as a ligand.

Ans) Due to lone pair on N in NH3.