关于热力学平衡判据的一些看法

根据热力学第二定律来判断系统的平衡态时,常用的判据有三个:熵判据、亥姆霍兹函数判据(最小亥姆霍兹函数原则)和吉布斯函数判据(最小吉布斯函数原则)。由于后两个判据可以看成是熵判据的推论,需要加以讨论的就是一个熵判据。在现行物理化学教材中,由于导出熵判据时未把“可逆过程”与“平衡态”这两个     

关于吉布斯-杜亥姆方程的推导

吉布斯 杜亥姆方程是物理化学及化学热力学中的主要方程 ,在处理溶液问题时有广泛的应用 ,由其出发还可导出马居耳 杜亥姆 (Margules Duhem)等主要公式。该方程的推导方法虽然简单 ,但是在国内外流行的 2 0余部物理化学及相关教材中 ,推导方法都有问题。笔者对此进行了探讨 ,指出了错误的原因 ,并提出了正确的处理方法。     

关于一些热力学公式使用条件的讨论

物理化学中的热力学公式在不同条件下有不同的衍变形式,极易诱导学生产生错误理解。通过实例分析,对热力学能和焓变化计算公式、赫姆霍兹自由能和吉布斯自由能判据、热力学基本方程等的使用和理解中存在的一些问题予以讨论。     

铁粉与氯气反应能生成二氯化铁吗?

从化学热力学基本原理出发,解释了在合适的反应温度下,铁粉与氯气反应生成三氯化铁的原因。并通过吉布斯-亥姆霍兹方程计算得出,在反应温度高于626 K时,铁粉与氯气反应将生成二氯化铁。这既体现了化学热力学对无机合成的指导意义,又可增强学生对化学热力学知识的理解和应用。     

毛细上升现象的热力学解释*

从热力学的角度讨论毛细上升平衡高度以及毛细上升现象中的能量转换与守恒。在毛细上升的始终态之间设计了可逆途径,计算了可逆毛细上升过程中系统的赫姆霍兹自由能减少值,系统克服重力以及外压做功的值,并根据能量守恒定律推导出了毛细上升平衡高度和球形曲面的拉普拉斯方程。该方法拓展了热力学在表面现象中的应用,并有利于学生理解毛细上升现象的能量来源。     

物理化学中的热力学方法、拓展及应用

主要依托物理化学中的热力学基本原理,浅议热力学方法、简介化工热力学方法和工程热力学方法及应用等。热力学方法主要有循环法、特性函数法、变量变换法、标准状态法、平衡法及极值法、微元法等,并归纳了各种方法的特点、作用及意义。对于学生学习物理化学中的热力学,具有一定的指导意义,拓展了热力学的基本知识。     

液面上大气泡形状的热力学证明

针对物理化学教材中的一道习题，对液面上形成的半球形大气泡进行分析，建立物理模型，提出简化假设，根据表面热力学原理，用数学方法给以证明，并绘出了相对表面吉布斯函数曲线。     

对由热力学基本方程推求可逆电池熵变的理解

常见的物理化学教材中,对可逆电池熵变的推求大都由热力学基本方程直接得到。结论是正确的,但笔者认为此推导过程欠妥。在教学过程中提出了对其完善的两种方法：一是采用状态函数法,二是利用在有非体积功存在的热力学基本方程进行演绎推理,通过合理的讨论分析,得出正确结论。     

关于熵判据、亥姆霍兹函数判据和吉布斯函数判据的讨论

通过理论推导和举出反例的方法,指出了熵增原理的应用限制。对亥姆霍兹函数判据和吉布斯函数判据也提出了应延伸其外延的教学建议。     

热力学量变换的教学研究

介绍了基于热力学偏微商关系的变量变换方法,讨论了在物理化学教学中的必要性及基本要求。     

Thermodynamic consideration of the mixed micelle of surfactants

In conformity with the conclusion obtained previously, the mixed micelle formation of surfactants was treated thermodynamically as the appearance of a macroscopic bulk phase with the aid of the excess thermodynamic quantities similar to those used for the adsorbed film. The composition of surfactant in the mixed micelle and the thermodynamic quantities of micelle formation were found to be evaluated by applying the thermodynamic equations derived. These equations were extended so as to be applicable to any kind of surfactant mixture. It was shown that the critical micelle concentration vs. composition of surfactant curves form a diagram analogous to the phase diagram of binary mixture. Applying the equation to the published data on typical surfactant systems, this thermodynamic approach was proved to be useful to clarify the miscibility of surfactants in the micellar state.     

Thermodynamic property predictions with the trebble-bishnoi equation of state

Predictions of thermodynamic properties including second virial coefficients, enthalpies, isobaric heat capacities, speed of sound, and Joule-Thomson coefficients are presented for the Trebble-Bishnoi equation of state. These predictions are compared both to experimental data and to predictions from the Peng-Robinson equation of state. Both equations of state give reasonable and consistent values for all of the above properties.     

Thermodynamic Foundation for High Temperature Electrochemistry

Thermodynamic concepts required for the thermodynamic calculation of the potentials of electrodes for high temperature applications are briefly reviewed. A thermodynamic approach to the calculation of half cell potentials and the standard chemical potential of an electron at high temperatures which are related to the Standard Hydrogen Electrode(SHE) is discussed. As examples, an external Ag/AgCl reference electrode and a YSZ(Ag|O2) pH sensor for high temperature applications are analyzed by using the thermodynamic ap-proach to derive a high temperature pH measurement equation. The two electrodes are employed to measure high temperature pH and the measured pH was compared with the calculated pH by using a solution chem-istry method. Concepts and principles for electrode kinetics are also briefly introduced and a modification to the Tafel equations is suggested.     

Studies on Thermodynamic Properties of Adsorption of Theophylline by Phenolic Resin Adsorbents

In the present work, the equilibrium adsorption of theophylline was studied by phenolic resin adsor-bents: JDW-2 (made by ourselves) and Duolite S-761 within a temperature range of 303--323 K. The experi-mental results show that the Freundlich adsorption law is applicable to the adsorption of theophylline on thetwo adsorbents, the exponents n＞l indicate that they are favorable to the adsorptions; the negative values ofall the isosteric adsorption enthalpies for the theophylline indicate the exothermic process of the adsorption,while the range(10—40 kJ/mol) of their magnitudes manifests the physisorption process; other thermody-namic properties, the free energy changes and the entropy change associated with adsorption have been calcu-lated from the Gibbs adsorption equation and the Gibbs-Helmholtz equation.     

单重态CCl~2与O~3反应的热力学及动力学性质研究

在量化计算的基础上运用统计热力学和Wigner校正的Eyring过渡态理论研究了不同温度下单重态CCl~2和臭氧O~3反应的热力学及动力学性质。计算结果表明该反应在低温下具有热力学优势,而在高温下具有动力学优势。     

New routes in the synthesis of metal oxides,I

Single crystals of numerous new metal oxides “rich in cations” are prepared by using methods such as dis- or conproportionation, thermal decomposition of higher valence oxides, or oxidation of metals and intermetallic compounds (“reactions with the wall”). Exchange reactions allow growth of single crystals even outside of thermodynamic equilibrium. The role of vacancies in structural chemistry as well as in “tailor-made” syntheses is emphasized and illustrated. Molecular aspects of solid state chemistry are demonstrated by cutting chains or rings and by dimerization of small entities. Many examples are provided.     

荧光淬灭和加强理论公式合理性的热力学分析

通过荧光法在不同温度下研究了3种第三代头孢新药: 盐酸头孢吡肟、头孢匹胺和头孢唑肟钠与人血清白蛋白(HSA)和牛血清白蛋白(BSA)的作用, 分别应用荧光淬灭和荧光加强理论公式计算了它们的结合常数等, 进而分别计算了它们的热力学函数. 因对应于不同的理论公式得出的K_A值并不完全相同, 由此得到它们相应的热力学参数也有所不同. 本文对这些热力学数据的差异进行了分析比较, 结果表明: 基于荧光加强理论公式(4)获得的热力学数据显示更为合理. 因而我们建议, 即使在研究受体-底物的荧光淬灭反应时, 采用荧光加强理论公式(4)可以获得更符合实际的结果.     

Thermodynamic issues associated with combined cyclic voltammetry and wafer curvature measurements in electrolytes

A thermodynamic framework has been provided for the interpretation of combined cyclic voltammetry and surface stress measurements, the latter being obtained from wafer curvature or beam deflection measurements of a solid electrode as a function of applied potential (so-called voltstressograms). Firstly, the derivation of electrocapillarity equations for solid electrodes has been critically reviewed by starting from the Gibbs adsorption equation appropriate for solid–electrolyte interfaces. This allowed us to demonstrate the critical importance of elastic surface strain in the thermodynamic boundary conditions of the partial derivatives intervening in the interpretation of voltstressograms. From these considerations, it was shown for the first time that the electrocapillarity equations for solid electrodes are not appropriate for describing the variation of surface stress with potential obtained from wafer curvature measurements, because such measurements are intrinsically incompatible with the constant strain condition implied in the electrocapillarity equations. An alternative explanation is provided for the experimentally observed proportionality between the current density, measured in cyclic voltammograms, and the first derivative of surface stress with respect to potential, obtained from voltstressograms.     

Correlations of Thermodynamic Properties of Aqueous Amino Acid-Electrolyte Mixtures

Suitable equations have been proposed to correlate thermodynamic properties, like mean ion activity coefficients, volumes and compressibilities, of amino acids in electrolyte solutions. An amino acid–electrolyte–water interaction parameter is extracted from the regression of the amino acid property values in aqueous electrolyte solution that is then transferred to an expression to correlate the properties of the electrolyte in mixtures. The single interaction parameter can successfully correlate the published data on mean ion activity coefficients, apparent molar volumes and compressibilities of amino acids as well as of electrolytes in their aqueous mixtures. The equations are tested against the large number of experimental data sets available in the literature.     

Thermodynamic functions for vibronic systems

A method is introduced which simplifies the derivation of equations for the calculation of statistical sums for vibronic systems. Within the “independent ordering approximation” analytical expressions are found for thermodynamic functions for molecules with degenerate electronic ground state (E?β and E ? e types of degeneracies). Vibronic interactions are shown to yield an additional thermodynamic stabilization. The computations were carried out for VCl₄ and VBr₄ with doubly degenerate electronic ground states. For these molecules the effect is shown to be small.