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为获得液体内压和摩尔定容热容的准确数据 ,以热力学状态方程和一个液体的 p-V-T方程为基础 ,提出了液体内压的计算方法以及如何由液体的摩尔定压热容推算摩尔定容热容。以包括极性液体、非极性液体和缔合液体的 13种液体为例 ,计算了它们在 2 5℃及 10 1.3 2 5 k Pa时的内压和摩尔定容热容。结果表明 :液体的内压达到 10 0 MPa数量级 ,从而导致液体摩尔定容热容与摩尔定压热容存在很大差异。若以摩尔定压热容的值代替摩尔定容热容 ,在上述 13种液体中的误差为 17%～ 5 6%范围以内。因此得出结论 :用液体摩尔定压热容的值代替摩尔定容热容的做法是错误的
In order to obtain accurate data of internal pressure and molar constant volume heat capacity, based on the thermodynamic equation of state and the pVT equation of a liquid, a method for calculating the internal pressure of the liquid and how to calculate the molar constant volume from the liquid’s molar constant pressure heat capacity Heat capacity. Taking 13 liquids including polar liquid, nonpolar liquid and associative liquid as examples, their internal pressure and molar constant volume heat capacity were calculated at 25 ℃ and 10 1.3 2 5 kPa. The results show that the internal pressure of the liquid reaches the order of 10 0 MPa, which leads to the great difference between the fixed molar heat capacity and the molar constant pressure heat capacity. If the value of molar constant pressure heat capacity instead of molar heat capacity, the error in the above-mentioned 13 kinds of liquids is within the range of 17% ~ 56%. Therefore concluded that: the use of liquid molar constant pressure heat capacity instead of molar constant volume heat capacity is wrong