Standard Molar Entropy - Chemistry

Chemistry

The standard molar entropy of a gas at STP includes contributions from:

  • The heat capacity of one mole of the solid from 0 K to the melting point (including heat absorbed in any changes between different crystal structures)
  • The latent heat of fusion of the solid.
  • The heat capacity of the liquid from the melting point to the boiling point.
  • The latent heat of vaporization of the liquid.
  • The heat capacity of the gas from the boiling point to room temperature.

Changes in entropy are associated with phase transitions and chemical reactions. Chemical equations make use of the standard molar entropy of reactants and products to find the standard entropy of reaction:

ΔS°rxn = S°products – S°reactants

The standard entropy of reaction helps determine whether the reaction will take place spontaneously. According to the second law of thermodynamics, a spontaneous reaction always results in an increase in total entropy of the system and its surroundings:

ΔStotal = ΔSsystem + ΔSsurroundings > 0

Read more about this topic:  Standard Molar Entropy

Famous quotes containing the word chemistry:

    “...some sort of false logic has crept into our schools, for the people whom I have seen doing housework or cooking know nothing of botany or chemistry, and the people who know botany and chemistry do not cook or sweep. The conclusion seems to be, if one knows chemistry she must not cook or do housework.”
    —Ellen Henrietta Swallow Richards (1842–1911)

    “If thought makes free, so does the moral sentiment. The mixtures of spiritual chemistry refuse to be analyzed.”
    —Ralph Waldo Emerson (1803–1882)

    “For me chemistry represented an indefinite cloud of future potentialities which enveloped my life to come in black volutes torn by fiery flashes, like those which had hidden Mount Sinai. Like Moses, from that cloud I expected my law, the principle of order in me, around me, and in the world.... I would watch the buds swell in spring, the mica glint in the granite, my own hands, and I would say to myself: “I will understand this, too, I will understand everything.””
    —Primo Levi (1919–1987)