Residual Entropy 3rd Law of Thermodynamics

[Nikhita_Jaaswal_2H]

In the textbook it highlights that the third law of thermodynamics states that at an absolute temperature of T=0, the entropy of the system approaches 0 because there is no positional or thermal disorder. How does the third law of thermodynamics hold true if there is still entropy in the system in the form of residual entropy?

[vsyacoubian2A]

There will always be some small amount of residual entropy, but as the system approaches 0K, the residual entropy will approach 0, but will never actually reach 0. Reaching 0K is currently physically impossible.

[Shelby Slaughter 3D]

But if 0K was reached would the residual entropy theoretically be zero, or still just infinitely small?

[Sebastian]

So theoretically what would higher entropy at 0k; a CO OR H2 molecule? Would they both have 0 entropy or would CO have some entropy due to its risidual entropy?

[Chem_Mod]

Residual entropy is possible only when molecules can have different orientations within the same crystal. For a perfect crystal (all molecules have the same orientation) the entropy is 0 at 0 K.