如何理解热力学基本公式适用条件

讨论了热力学基本公式适用条件的本质原因。解释了相变和化学变化过程的状态函数计算为何要设计可逆过程。     

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。     

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。     

高温高压Li3N-hBN体系cBN转变的热力学分析

以经典热力学第二定律ΔG<0为依据,分析了静态高温高压触媒法合成立方氮化硼(cBN)过程中发生的可能反应.考虑温度和压强对反应物相体积的影响,计算了六方氮化硼(Li3N-hBN)体系中hBN+Li3N→Li3BN2,h BN→cBN及Li3BN2→Li3N+cBN反应在高温高压条件下的ΔG.结果证实,Li3BN2由Li3N与hBN在高温高压(T>1300 K,P>3.0 GPa)条件下反应得到,在cBN的合成(T=1600～1800 K,P=4.6～6.0 GPa)条件下,hBN和Li3BN2都有向cBN转化的倾向,但由hBN向cBN直接转变的反应自由能比Li3BN2分解生成cBN的反应自由能更负,反应的可能性更大.探讨了高温高压条件下立方氮化硼的转变机理。     

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。     

理想气体绝热过程方程的4种推导*

物理化学的一个重要魅力是公式的交互关联性。以理想气体绝热过程方程为例,详细地叙述了如何从热力学第一定律、熵差计算公式、偏微分和全微分等4个不同的起点出发,利用必要的热力学关系,最后到达相同的终点的推演过程。     

不同类型化学平衡的热力学本质

探讨了定温定容下气相化学平衡、复相化学平衡和纯凝相化学平衡的热力学本质。指出,对于不同类型的反应,建立化学平衡的根本原因其实是不相同的,不能简单地都归因于混合过程对系统Gibbs自由能的影响。     

高纯铌的脱氧热力学特性

在 973- 1 473K温度范围内 ,测定了铌与Ca CaO和与Mg MgO共存时铌金属中氧的平衡浓度 .得出并讨论了铌中的氧溶解反应的Gibbs自由能表达式和氧分压 温度 成分 (p t x)关系表达式 .     

粉笔分离菠菜色素实验条件优化*

采用家用超声波眼镜清洗机辅助提取菠菜色素,考察了菠菜自身水分、不同提取部位、不同提取溶剂以及不同石油醚乙酸乙酯体积比对提取物粉笔分离效果的影响。实验结果表明:干燥菠菜叶、丙酮提取、V_石油醚∶V_乙酸乙酯=17∶2展开时,粉笔分离后呈现出5条清晰的分离色带。改进后实验效果更好,植物成分提取和色谱分离的教学功能更有利于实现。     

水的离子积pKw=f(T.P)计算公式

本文在系统地研究了国内外水的离子积计算公式基础上,根据化学热力学理论,提出临界区和超临界区水的离子积pK_W=f(T.P)计算公式。与Sweeton实验值比较,0°～300℃pK_W平均偏差0.008;0°～300℃,1—1000bar pK_W计算值接近Marshall公式的计算值,但比它实用。同时,可以导出pK_W=f(T)pK_W=f(T.ρ)类型的计算公式。     

规范不同均相化学反应的热力学性质表示及其关系

尝试对均相化学反应的热力学性质表述进行规范,如浓度的表示形式、不同标准状态、B组分标准状态化学势μBo、标准吉布斯自由能变化量△rGm,ao、平衡常数Kao、反应的热效应△rHm,ao等。     

Thermodynamic Analysis of the Adsorption and Micellization Activity of the Mixtures of Rhamnolipid and Surfactin with Triton X-165

The surface tension of aqueous solutions of Triton X-165 with rhamnolipid or surfactin mixtures was measured. The obtained results were applied for the determination of the concentration and composition of the Triton X-165 and biosurfactants mixture at the water–air interface as well as the contribution of the particular component of the mixtures to water surface tension reduction and the mutual influence of these components on the critical micelle concentration. The determination of these quantities was based on both the commonly used concepts and a new one proposed by us, which assumes that the composition of the mixed monolayer at the water–air interface depends directly on the pressure of the monolayer of the single mixture component and allows us to determine the surface concentration of each mixture component independently of surface tension isotherms shape. Taking into account the composition of the mixed monolayer at the water–air interface, the standard Gibbs adsorption free energy was considered. The obtained results allow us to state that the concentration of both mixture components corresponding to their saturated monolayer and the surface tension of their aqueous solution can be predicted using the surfactants’ single monolayer pressure and their mole fraction in the mixed monolayer determined in the proposed way.     

醚基功能化离子液体[MOEMIm]Cl和[EOEMIm]Cl热力学性质

通过核磁共振氢谱,核磁共振碳谱,元素分析和热重分析对醚基功能化的离子液体[MOEMIm]Cl和[EOEMIm]Cl进行了表征。在温度范围T=288.15–328.15 K内,测定了离子液体[MOEMIm]Cl和[EOEMIm]Cl的密度(ρ)、表面张力(γ)和折光率(nD)。根据这些实验数据,讨论并计算了离子液体[MOEMIm]Cl和[EOEMIm]Cl的体积性质。计算出离子液体[MOEMIm]Cl和[EOEMIm]Cl的摩尔表面吉布斯自由能(gs)、摩尔表面熵(s)、摩尔表面焓(h)、摩尔极化度(Rm)和摩尔极化率(αp),h均近似为一个常数说明这两种离子液体从内部到表面的过程是一个等库仑过程,同时这两种离子液体的Rm和αp均与温度无关。本文还用摩尔表面Gibbs自由能改进Lorentz-Lorenz方程并预测离子液体表面张力,预测值与实验值高度相关。     

C_8芳烃异构体+异丙醇体系在333.15K时的过量摩尔Gibbs自由能

采用CP-I型汽液平衡双循环釜,测定了333.15 K时乙苯+异丙醇、邻二甲苯+异丙醇、间二甲苯+异丙醇、对二甲苯+异丙醇四个体系的汽液平衡数据,计算了该温度下四个体系的过量摩尔Gibbs自由能,并对所测数据进行了恒温下热力学一致性检验。用Wilson方程关联了实验数据,拟合精度令人满意。     

吡啶基离子液体[C_6py][DCA]热力学性质及利用新E?tv?s方程预测其表面张力

制备了吡啶类离子液体N-己基吡啶二氰胺盐[C_6py][DCA],并用核磁共振氢谱(~1H NMR)、核磁共振碳谱(~(13)C NMR)、差热扫描量热(DSC)、傅里叶变换红外(FT-IR)光谱对其进行表征。在288.15–338.15 K温度范围内,采用标准加入法,测定其密度(ρ)、表面张力(γ)和折光率(n_D)。在测得的实验数据的基础上,得到了离子液体[C_6py][DCA]的分子体积(V_m)、表面能(E_a)、摩尔极化度(R_m)和极化率(α_p)。结果显示E_a、R_m和α_p几乎不随温度的变化而发生改变。本文还提出了摩尔表面Gibbs自由能(g_s)的概念,并改进了E?tv?s方程。同时还计算了gs、临界温度(T_c)和E?tv?s方程经验参数(kE),并预测了离子液体[C_6py][DCA]的表面张力,预测值与实验值具有较好的一致性。     

Thermodynamic stability of AuSe at temperature from (400 to 700) K by a solid state galvanic cell

The numerical values on the standard thermodynamic functions of AuSe were determined by the electromotive force (EMF) method in a solid-state galvanic cell with a superionic conductor AgI as the solid electrolyte. According to the experimental data on the EMF vs. temperature, the analytical equations for Gibbs free energy, enthalpy and entropy were obtained for the single stable polymorphic form of AuSe. The temperature-dependent relationships of Gibbs free energy of formation of AuSe and the standard thermodynamic functions of compounds within the temperature range (400 to 700) K were also evaluated. No α–β transformation was identified in the gold saturation and β-form is a metastable modification of AuSe.     

利用统计缔合流体理论状态方程预测混合气体水合物的平衡形成条件

利用统计缔合流体理论(SAFT)状态方程结合van der Waals-Platteeuw统计力学模型用于预测含有甲烷、乙烷、丙烷、乙烯、丙烯、H₂S, CO₂, N₂和H₂二元气体水合物的平衡形成条件. 对于气相和液相, 应用SAFT方程来描述. 在气相和液相相平衡的模拟过程中, SAFT方程考虑了硬球斥力、成链力、色散力以及缔合相互作用. 对于水合物相, 采用van der Waals-Platteuw模型来计算. 该方法的预测结果与实验数据吻合.     

On the Use of Thermodynamic Cycles for the Calculation of Standard Potentials for the Oxidation of Solid Metals in Solution

The performance of a thermodynamic cycle for the calculation of the standard reduction potential (SRP) of a series of metals is examined. It is found that the introduction of simple entropic corrections substantially improves the agreement with experimental data. The accuracy of the estimations is in the range of 0.04 V, which opens the possibility to calculate the SRP for metals in non-aqueous solvents or other unusual situations.     

Meaning and Measurability of Single‐Ion Activities,the Thermodynamic Foundations of pH,and the Gibbs Free Energy for the Transfer of Ions between Dissimilar Materials

Considering the relationship between concentration and vapor pressure (or the relationship between concentration and fugacity) single‐ion activity coefficients are definable in purely thermodynamic terms. The measurement process involves measuring a contact potential between a solution and an external electrode. Contact potentials are measurable by using thermodynamically reversible processes. Extrapolation of an equation to zero concentration and ionic strength enables determination of single‐ion activity coefficients. Single‐ion activities can be defined and measured without using any extra‐thermodynamic assumptions, concepts, or measurements. This method could serve as a gold standard for the validation of extra‐thermodynamic methods for determining single‐ion activities. Furthermore, it places the concept of pH on a thermodynamically solid foundation. Contact potential measurements can also be used to determine the Gibbs free energy for the transfer of ions between dissimilar materials.     

A novel approach to the calculation of the free energy due to molecular flexibility

The contribution of the molecular flexibility to the solvation excess free energy is expressed in terms of probabilities of reaching hard limits on intramolecular coordinates in a series of calculations successively relaxing those limits. Numerical tests on the harmonic oscillator are also presented and used to make suggestion about computational issues.