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单词 standard state
释义
standard state

Physics
  • A state of a system used as a reference value in thermodynamic measurements. Standard states involve a reference value of pressure (usually one atmosphere, 101.325 kPa) or concentration (usually 1 M). Thermodynamic functions are designated as ‘standard’ when they refer to changes in which reactants and products are all in their standard and their normal physical state. For example, the standard molar enthalpy of formation of water at 298 K is the enthalpy change for the reaction

    H2(g)+½O2(g)H2O(l)ΔH298=-285.83kJ mol-1.

    Note the superscript is used to denote standard state and the temperature should be indicated.


Chemistry
  • A state of a system used as a reference value in thermodynamic measurements. Standard states involve a reference value of pressure (usually one atmosphere, 101.325 kPa) or concentration (usually 1 M). Thermodynamic functions are designated as ‘standard’ when they refer to changes in which reactants and products are all in their standard and their normal physical state. For example, the standard molar enthalpy of formation of water at 298 K is the enthalpy change for the reaction

    H2(g)+½O2(g)H2O(l)

    Δ‎H298=–285.83 kJ mol−1. Note the superscript is used to denote standard state and the temperature should be indicated.


Chemical Engineering
  • A state of a system used as a thermodynamic reference point. Reference points are usually taken as a temperature of 298.15K, a pressure of 101.325 kPa, and concentration of 1 M. The standard state is denoted by the superscript symbol ο. For example, the standard molar heat of formation of water in the reaction:

    H2(g)+1/2O2(g)H2Ol is ΔHfο is -286 kJ mol-1
    .


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