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The standard molar entropy at pressure = is usually given the symbol S°, and has units of joules per mole per kelvin (J⋅mol −1 ⋅K −1). Unlike standard enthalpies of formation, the value of S° is absolute. That is, an element in its standard state has a definite, nonzero value of S at room temperature.
Absolute entropy of strontium. The solid line refers to the entropy of strontium in its normal standard state at 1 atm pressure. The dashed line refers to the entropy of strontium vapor in a non-physical state. The standard entropy change for the formation of a compound from the elements, or for any standard reaction is designated ΔS° form or ...
The standard state of a material (pure substance, mixture or solution) is a reference point used to calculate its properties under different conditions.A degree sign (°) or a superscript Plimsoll symbol (⦵) is used to designate a thermodynamic quantity in the standard state, such as change in enthalpy (ΔH°), change in entropy (ΔS°), or change in Gibbs free energy (ΔG°).
Unlike many other functions of state, entropy cannot be directly observed but must be calculated. Absolute standard molar entropy of a substance can be calculated from the measured temperature dependence of its heat capacity. The molar entropy of ions is obtained as a difference in entropy from a reference state defined as zero entropy.
Molar Gibbs free energy is commonly referred to as chemical potential, symbolized by , particularly when discussing a partial molar Gibbs free energy for a component in a mixture. For the characterization of substances or reactions, tables usually report the molar properties referred to a standard state .
Std entropy change of vaporization, Δ vap S o: 113 J/(mol·K) Solid properties Std enthalpy change of formation, Δ f H o solid? kJ/mol Standard molar entropy, S o solid? J/(mol K) Heat capacity, c p? J/(mol K) Liquid properties Std enthalpy change of formation, Δ f H o liquid: −238.4 kJ/mol Standard molar entropy, S o liquid: 127.2 J/(mol ...
Std entropy change of vaporization, Δ vap S o +97.41 J/(mol·K) at BP of −33.4 °C Solid properties Std enthalpy change of formation, Δ f H o solid? kJ/mol Standard molar entropy, S o solid? J/(mol K) Heat capacity, c p? J/(mol K) Liquid properties Std enthalpy change of formation, Δ f H o liquid: −80.882 ± 0.053 kJ/mol [2] Standard ...
Standard molar entropy, S o solid? J/(mol K) Heat capacity, c p? J/(mol K) Liquid properties Std enthalpy change of formation, Δ f H o liquid? kJ/mol Standard molar entropy, S o liquid: 126.7 J/(mol K) Heat capacity, c p: 68.5 J/(mol K) at −179 °C Gas properties Std enthalpy change of formation, Δ f H o gas: −83.8 kJ/mol Standard molar ...