偏摩尔量加和公式可能的两处新应用

本文探讨了偏摩尔量加和公式的两处新的应用。其中之一应用于摩尔反应吉布斯自由能与化学势关系式的推解,另一应用于离子活度关系式的推解。在这两个关系式的推解过程中若采用偏摩尔量的加和公式,不仅可以使两个关系式的物理概念更加明晰,推导更加合理化,也可以使这两个关系式的适用环境更易被人接受和理解。     

谈谈化学计算的关系式法

关系式法,已经被公认是一种简便可行的化学计算方法。但是,这种方法还欠成熟,对关系式、关系式法的概念还不甚明确,看法也不统一。本文拟谈谈个人学习、运用关系式法的体会,以期引起同行的讨论,使关系式法臻于完善。     

关于稀释定律的一点补充

对于弱酸或弱碱,溶液的电离度与其浓度平方根成反比,即浓度越稀,电离度越大,这个关系式叫作稀释定律,可表示为α=(K/C)~(1/2)。从上式可以看出,当无限稀释时,C→0,则α→∞。很明显,这一结论是不合理的。这说明稀释定律的关系式是有条件的,当无限稀释时,该关系式已不再适用。本文对极稀溶液中一元、二元弱酸电离度的关系式进行了推导。根据所得的新关系式可发现,在无限     

核酸、蛋白质的电荷数随pH的变化规律

从理论上推导出核酸、蛋白质的正电荷数随pH的变化关系式:Y=∑(i=1-3)[H^+]~n~i/([H^+]+K~b~i),负电荷数随pH的变化关系式:X=∑(i=1-5)K~a~im~i/([H^+]+k~a~i)、净电荷数随pH变化关系式以及等电点计算关系式,并从关系式中导出核苷酸、碱基、中性氨基酸、酸性氨基酸、碱性氨基酸的等电点关系式,表明理论推导是正确、可靠的。用表面活性剂沉淀肌酸激酶、不同pH的溶菌酶电泳方法验证了计算结果的可靠性。同时,计算了人DNA、蚕DNA、β-乳球蛋白带电荷数随pH的变化规律,并估计了计算误差。     

关于Mayer关系式和热容比关系式的再讨论

对热力学中关于均匀物质的等压热容(Cp)和等容热容(CV)的2个重要关系式(Mayer关系式和热容比关系式)进行了比较全面的分析和讨论,总结了在教学过程中应该注意的相关事项,以期对教和学都有所裨益。     

论中国地震震级与震中烈度的关系及其应用

本文利用57次地震的M,I_0,h资料,计算给出了中国地震震级与震中烈度及其震源深度关系的修正式;分析了华北地区几次大地震的前震和余震资料,分别计算给出前震、余震的震级与震中烈度的关系式;同时计算给出新丰江水库地震的这种关系式.对比表明:前震、余震和水库地震各有其本身的震级与震中烈度的关系式,与一般地震(主震)的这个关系式有系统的差别。     

由溶度积计算溶解度问题的商榷

在国内外一些大一无机化学中,难溶物质的溶度积(Ksp)和溶解度(S)常用表1罗列的关系式相互求算。一些课本在处理这部分内容时,只讲关系式,不讲这些关系式的应用条件;只讲近似计算,不讲准确(系统)计算;只讲特殊情况,不讲一般情况。     

多组分体系相图中的杠杆原理形式

讨论了两相和三相多组分体系中杠杆原理的两种形式。对两组分体系,利用三相线上的杠杆原理关系式和凝固点降低公式,解释了熔化物体系冷却过程中的步冷曲线。另外,还讨论了三组分体系相图中,同一直线段上三个物系点之间的类杠杆原理关系式。该关系式可以用于不同浓度溶液的配制和三相体系相图的绘制。     

热力学函数关系式教学难点的化解

分4个层次介绍物理化学课程中热力学函数关系式的教学方法,探讨了运用基本公式和偏微商关系进行推导的方法,并举例说明了热力学函数关系式在处理实际问题时的应用。     

液固吸附色谱中溶质保留值与流动相组成关系的研究Ⅰ.二元流动相体系

本文在Snyder吸附顶替模型基础上考虑溶质分子与溶剂之间的相互作用,并用溶解度参数理论推出溶质保留值与流动相组成的关系式:logk′=B_0+B_1Φ+B_2Φ~2+B_3logΦ。实验证明了此关系式的正确性,同时考察了关系式中系数B_0、B_3及其物理意义。与其它模型比较以本文的方法误差最小。     

Molecular dynamics simulation studies of the conformation and lateral mobility of a charged adsorbate biomolecule: implications for estimating the critical value of the radius of a pore in porous media

The conformations, the values of the lateral transport coefficient of a charged biomolecule (desmopressin) in the adsorbed layer and in the liquid layers above the adsorbed layer, the potential energies of the interaction between the biomolecules located in different liquid layers with the charged solid surface and with the biomolecules in the adsorbed layer, the potential energies of the interaction between water molecules in the hydration layers surrounding the conformations of the biomolecules in different layers, as well as the structure and number of hydration layers between the different conformations of desmopressin, were determined by molecular dynamics simulation studies. The results show that the lateral mobility of the adsorbed desmopressin is approximately equal to zero and the value of the lateral transport coefficient of the biomolecule in the liquid layers located above the adsorbed layer increases as the distance of the liquid layer from the charged solid surface increases. But the values of the lateral transport coefficient of the biomolecule in the liquid layers above the adsorbed layer are lower in magnitude than the value of the transport coefficient of desmopressin along the direction normal to the charged solid surface in the liquid phase located above the vacant charged sites of the solid surface, and these differences in the values of the transport coefficients have important implications with respect to the replenishment of the biomolecules in the inner parts of a channel (pore), the overall rate of adsorption, and the form of the constitutive equations that would have to be used in macroscopic models to describe the mechanisms of mass transfer and adsorption in the pores of adsorbent media. Furthermore, a novel method is presented in this work that utilizes the information about the sizes of the conformations of the biomolecule in the adsorbed layer and in the liquid layers above the adsorbed layer along the direction that is normal to the charged solid surface, as well as the number and size of the hydration layers along the same direction, and could be used to estimate the value of the lower bound of the linear characteristic dimension of a pore (i.e., pore radius) in porous adsorbent media (e.g., porous adsorbent particles; skeletons of porous monoliths) in order to realize effective transport and overall adsorption rate.     

Energy contribution of the solvent to the charge migration in DNA

The authors have investigated the interactions of the reaction centers, participating in the charge transfer reaction within the DNA molecule with the phosphate backbones and the solvent molecules, and have estimated the contribution of these interactions into the charge migration in DNA. They have determined the unequal shift of the energy surfaces of the initial and final transition states of the transfer reaction along the energy axis and the dependence of the magnitude of the energy shift on the nature of the reaction centers and the surrounding environment. The nonuniform distribution of the negative charge in the DNA phosphate backbones results in an increase of the positive shift of the energy surface of the DNA base pairs in the center of the structure, where the maximum density of the negative charge is concentrated. Localization of the positive charge on the guanine and the adenine in the DNA base pairs in the oxidized state results in a dependence of the free energy of reaction in the solvent on the pair sequences and their arrangement in the DNA chain. As an example, for the G-C/A-T configuration the positive charges are localized on the same strand that results in a decrease of the free energy of reaction in the solvent for charge migration from G-C to A-T pair by 0.125 eV.     

Effect of structural factors on the disintegration of the molecular ions of nitrophenylisoxazoles during electron impact

The dissociative ionization of some nitrophenylisoxazoles was investigated. The effect of the energy of the ionizing electrons and the temperature of the inlet system on the elimination of NO by the molecular ion is examined. On the basis of a comparison of the intensities of the peaks of the (M-NO)⁺ ions, the presence of a correlation between the probability of detachment of NO from the molecular ion and the stability of the cyclic conjugated structures with localization of the charge on the oxygen atom is demonstrated.     

Cathode of a hydrogen-oxygen fuel cell with a solid polymer electrolyte: The effect of the flooding of pores by water on the characteristics of the active layer

A computer model of the active layer of the cathode of a hydrogen-oxygen fuel cell with a solid polymer electrolyte is studied. The active mass of the electrode consists of equidimensional grains of the substrate (agglomerates of carbon particles with platinum particles embedded in them) and a solid polymer electrolyte (Nafion). The flooding by water can be experienced by both the pores in the substrate grains, which facilitate the oxygen penetration into the active layer of the electrode, and the voids between the grains. All possible versions of the flooding of these pores by water are considered. A calculation of the optimum, at a given polarization of the electrode, value of electrochemical activity, the thickness of the active layer, and the weight of platinum is performed. The major parameters of the system are the concentrations of grains of the substrate and solid polymer electrolyte, the size of these grains, the platinum concentration in the substrate grains, the average diameter of pores in the substrate grains, and the polarization of electrodes. The ultimate aim of the work is to estimate how the flooding of pores of the active layer of the cathode by water affects the magnitude of the optimum current, the effective thickness of the active layer, and the weight of platinum.Translated from Elektrokhimiya, Vol. 41, No. 1, 2005, pp. 35–47.Original Russian Text Copyright © 2005 by Chirkov, Rostokin.     

Complex conductivity of water-saturated packs of glass beads

The low-frequency conductivity response of water-saturated packs of glass beads reflects a combination of two processes. One process corresponds to the polarization of the mineral/water interface coating the surface of the grains. The other process corresponds to the Maxwell-Wagner polarization associated with accumulation of the electrical charges in the pore space of the composite medium. A model of low-frequency conductivity dispersion is proposed. This model is connected to a triple-layer model of electrochemical processes occurring at the surface of silica. This model accounts for the partition of the counterions between the Stern and the diffuse layers. The polarization of the mineral/water interface is modeled by the electrochemical polarization model of Schurr for a spherical grain. We take into account also the DC surface conductivity contribution of protons of the sorbed water and the contribution of the diffuse layer. At the scale of a macroscopic representative elementary volume of the porous material, the electrochemical polarization of a single grain is convoluted with the grain size distribution of the porous material. Finally, the Maxwell-Wagner polarization is modeled using the complex conductivity of a granular porous medium obtained from the differential effective medium theory. The predictions of this model agree well with experimental data of spectral induced polarization. Two peaks are observed at low frequencies in the spectrum of the phase. The first peak corresponds to the distribution of the size of the beads and the second peak is due to the roughness of the grains.     

Water-soluble polyelectrolyte complexes of pyridine-containing polyphenylene dendrimers

The sizes of soluble polyelectrolyte complexes formed through mixing of solutions of dimethyl sulfate-alkylated rigid pyridine-containing polyphenylene dendrimers of various generations with the solution of sodium polystyrenesulfonate are measured with the use of dynamic light scattering. Effects of the length of the polyanion chain of the dendrimer, the generation number of the dendrimer, and the charge ratio of polymer components on the sizes of the complexes are examined. The results of this study are in agreement with the theoretical analysis of interaction between the charged dendrimer and the polyelectrolyte of the opposite charge sign and suggest the spontaneous formation of nanosized particles of water-soluble complexes.     

学科能力导向的“物质构成的奥秘”教学研究

以王磊提出的化学学科能力框架为理论依据,对“物质构成的奥秘”主题进行分析,从核心知识经验、认识角度思路、认识对象及问题、能力活动要素等4个维度构建了“物质构成的奥秘”主题的学科能力模型。运用实验法进行教学实践,证实了本研究设计的教学方式更有利于学生学科能力的发展提升。最后提出学科能力导向的“物质构成的奥秘”教学设计模式和教学实施的有效策略:(1)单元整体系统化设计,有层次有梯度的发展学生学科能力;(2)侧重应用实践型任务的解决,外显知识的输出性功能和价值;(3)重视核心知识和认识角度的建立过程;(4)追问、外显学生的认识角度和认识思路。     

Mass spectra of 1- and 2a-substituted 1,3,5,7-tetramethyl-2,4,6,8-tetrathiaadamantanes

A comparative analysis was made of the mass spectra of monosubstituted 1,3,5,7-tetramethyl-2,4,6,8-tetrathiaadamantanes (TMITA). It is shown that the pathways of monomolecular fragmentation depend on the character of the substituent and the isomeric form of the TMTTA. The principal lines in the mass spectra of the investigated compounds indicate the occurrence of competitive processes of fragmentation of the molecular ions (M⁺) with detachment of the substituent from the M⁺ ion or with cleavage of the cellular structure. The first process makes it possible to form a judgement regarding the mechanism of the fragmentation of the molecular ion and the site of primary localization of the charge on the fragment ions as a function of the donor—acceptor properties of the substituents, and the second process enables one to form a judgement regarding the character of the fragmentation of the cellular structures of the various isomeric forms.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 748–752, June, 1978.     

Effect of SDBS solution on the surface potential properties of the Zhaozhuang coal

It is of great significance to study the effect of surfactants on the coal surface potential for effective dust suppression in mining faces. The effect of different concentrations of sodium dodecyl benzene sulfonate (SDBS) solution on the surface potential of the Zhaozhuang coal was measured by atomic force microscopy (AFM). The experimental results show that the SDBS solution has significant influence on the surface potential of the Zhaozhuang coal. The electrical characteristics of the coal surface at the nanometer scale are different from those of macroscopic or the mesoscopic level. The surface potential of coal is basically a normal distribution, showing certain electrical characteristics. The mean value of the surface potential of the Zhaozhuang coal is increased with the increase in concentration of the SDBS solution; when the concentration of the SDBS solution is 0.3%, the mean value of surface potential is 5.59 mv, which is about two times of the mean value of the surface potential without SDBS solution added. With the increase of the concentration of the SDBS solution, the maximum value of the surface potential of the Zhaozhuang coal increases, and the minimum value decreases. It shows that the SDBS solution has a significant effect on the potential distribution law and the magnitude of the coal surface. Subsequently, on the basis of the constructed Zhaozhuang coal macromolecule model, xtb and Multiwfn simulation software were used to calculate the molecular surface electrostatic potential value and electron density value of the Zhaozhuang coal molecules after adding water molecules. The variation law for the electrostatic potential surface of the molecule was obtained after adding numbers of water molecules to the surface of the coal molecule. The simulation results show that the area proportion of absolute molecular surface electrostatic potential greater than 10 kcal/mol is increased with the growth in the number of water molecules, while the area proportion of absolute molecular surface electrostatic potential less than 10 kcal/mol is decreased. Because of the free state O─H bond polarity of water molecules, the charges on the molecular surface are rearranged in order to change the electron density on the surface of coal molecules, which affects the overall electrostatic potential of the configuration.