Question

which one of the following is a molecular crystal
A) Rock salt
B) Dry ice
C) Diamond
D) quartz

Answer 1

ANSWER:

Dry Ice  

EXPLANATION:  

   Molecular crystalline solids comprises molecules that are held together by dipole-dipole, dispersion, and hydrogen-bond inter-particle forces. These are all inter-molecular forces that are much weaker than intra-molecular forces like ionic bonds. "Molecular crystalline solids" are comparatively soft, low in density, make poor thermal and electrical conductors and have low-moderate melting points, generally less than 300°C.

  Common instances comprise ice ($H_{2} O$) and dry ice ($CO_{2}$).Dry ice has very weak bonds because of which it sublimates directly from a solid to a gas at -78.5°C.. Fry Ice is a molecular crystal wherein the crystal lattice comprises molecules of $CO_{2}$ instead of individual oxygen/carbon atoms.