• The entropy of a pure crystalline substance at absolute zero is defined to be equal to zero.
  • As the temperature of the substance increases, its entropy increases because of an increase in molecular motion.
  • The entropy change for a reaction can be determined if the standard entropies of each substance are known.
  • The units for entropy are J/K • mol.
  • Standard entropie for a few substances are shown in the Table below:Standard Entropy Values at 25°C.
  • The symbol for entropy is  and the standard entropy of is given by the symbol , indicating that thestandard entropy is determined under standard conditions.
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