The absolute standard entropy of atom X(g) is 100 J/K

Question

The absolute standard entropy of atom X(g) is 100 J/K • mol. Which is a reasonable value for the absolute standard entropy of X₂(g)? A) 200 J/K • mol B) 170 J/K • mol C) 100 J/K • mol D) 80 J/K • mol E) 50 J/K • mol

Quizplus · Accepted Answer

The absolute standard entropy of the compound X₂(g) is likely to be higher than that of the atom X(g) due to the presence of multiple atoms in the compound. However, the value is unlikely to double to 200 J/K • mol, so A can be ruled out. The compound contains sulfur and boron, which are relatively heavy elements with many possible vibrations and rotations, so it is reasonable to assume that the entropy would be higher than that of lighter elements. Based on these factors, B (170 J/K • mol) seems like the most reasonable option. C (100 J/K • mol) cannot be ruled out entirely, but it is unlikely that the entropy would remain the same for the compound as it was for the single atom. D (80 J/K • mol) and E (50 J/K • mol) are unlikely to be high enough to account for the multiple atoms and heavier elements in the compound.