Chemistry - Complete P-block Question with Solution | TestHub

(A) is correct: Red phosphorus is more stable than white phosphorus because white phosphorus has high angular strain in its P₄ tetrahedral structure.

(B) is correct: Graphite is the most thermodynamically stable allotrope of carbon at standard temperature and pressure.

(C) is incorrect: The melting point of HI ($189.3K$) is higher than that of HF ($189.6K$) due to significantly stronger London dispersion forces.

(D) is incorrect: SbH₃ has a higher boiling point than NH₃ because its larger size leads to stronger van der Waals forces that outweigh the hydrogen bonding in NH₃.