Standard Molar Entropies

Because the entropyA thermodynamic state function, symbol S, that equals the reversible heat energy transfer divided by temperature; higher entropy corresponds to greater dispersal of energy on the molecular scale. See also standard entropy. of a substanceA material that is either an element or that has a fixed ratio of elements in its chemical formula. depends on the amount of substance, the pressureForce per unit area; in gases arising from the force exerted by collisions of gas molecules with the wall of the container., and the temperatureA physical property that indicates whether one object can transfer thermal energy to another object., it is convenient to describe the entropy of a substance in terms of S_m°, its standard molar entropy, i.e., as the entropy of 1 mol of substance at the standard pressure of 1 atmAbbreviation for atmosphere, a unit of pressure equal to 101.325 kPa or 760 mmHg. (101.3 kPa) and given temperature. Values of the standard molar entropies of various substances at 298 K (25°C) are given in the table. A table like this can be used in much the same way as a table of standard enthalpies of formation in order to find the entropy change ΔS_m° for a reaction occurring at standard pressure and at 298 K.

The Standard Molar Entropies of Selected Substances at 298.15 K (25°C)