The Third Law of Thermodynamics postulates that absolute entropy of a perfectly ordered crystal at 0 — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

Residual entropy occurs when a molecule can adopt multiple nearly-equivalent orientations in the crystal lattice at absolute zero, freezing into a disordered state. $CO$ (which can orient as CO or OC), $N_2O$, and ice exhibit this. Perfectly symmetric $CO_2$ obeys the Third Law strictly.