Question

The standard absolute entropy of a substance, (${S^o}$) is the entropy of the substance in its standard state at 1 atm, temperature being (in K)

Answer 1

Here, in the question standard temperature (in K) is asked at which standard absolute entropy exists. Recall the standard temperature and pressure conditions, also called STP conditions. At STP conditions, the state of a substance is the most stable, also called standard state.

Complete step by step answer:
Entropy can be defined as a measure of degree of randomness or disorder in a system or it can also be thought as a relative distribution of the energy within the system. A perfect crystal at absolute temperature i.e., 0 K, is in state of minimum entropy because each atom is fixed at a particular position in the crystal lattice. Entropy of a pure perfect crystalline substance is zero at absolute zero.
Standard absolute entropy is defined as the absolute entropy of a substance in its standard state that is, at atmospheric pressure 1 atm and temperature being 298.15 K or ${25^o}C$. Standard absolute entropy is represented by the symbol ${S^o}$. Unit of standard absolute entropy is $J{K^{ - 1}}mo{l^{ - 1}}$.
In this question we are only asked about standard temperature at which standard absolute entropy exists and therefore, the answer is 298.15 K or we can simply say 298 K.

Note: It should be noted that generally, gases possess large positive values of ${S^o}$ because gas molecules are chaotically and randomly distributed. Solids possess smaller positive values of ${S^o}$ because in solids, intermolecular forces are large and hence, atoms are less randomly distributed or possess negligible randomness.