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1.
将讨论式教学法的基本思想应用到物理化学的课堂教学中,对物理化学的教学难点--热力学自发过程总熵判据的适用条件问题进行了深入的讨论,最终归纳总结,得出重要结论:总熵判据只能用来判断过程的可逆性,不能直接判断过程的自发性。要想进一步判断过程的自发性质,须结合系统与环境之间交换的总功进行判断。通过讨论式教学实践,学生对热力学自发过程总熵判据的适用条件有了更加深入的理解,给后续课程的学习打下了良好的基础。 相似文献
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文章指出现有各种自发过程的判据都是在指定的约束条件下才能应用,缺乏普适性是自发过程定义多样化的引发原因。在无约束条件下将热力学第一定律代入总熵判据得出并分析讨论了总熵判据的另一种形式,结合自发过程的特点总结出了热力学变化过程中能量变化的本质,给出了自发过程的通用定义。进一步指出原总熵判据只能分辨可逆与不可逆,不能分辨自发与非自发。文章给出的总熵判据的另一种形式——封闭系统任意过程的做功能力判据具有分辨自发与非自发的能力。通过理论研讨和实际应用表明,做功能力判据与总熵判据完全等价,在相应约束条件下可还原为当前热力学中各类方向判据。填补了常见的变温过程和变压过程在以前的教科书中无自发和非自发判据的空白。以前教科书中由于自发过程定义和解释的混乱而出现的一些疑难问题,在通用定义和做功能力判据面前都能得到满意的解答。 相似文献
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介绍了国内物理化学教材中“熵增原理”的不同表述,对△S隔离≥0(〉0不可逆,自发;=0可逆,平衡)的表述提出了不同的意见。 相似文献
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势力学第二定律的核心内容熵判据有多种形式,应用时常易造成混淆。在对熵判据多种形式的讨论基础上指出,熵判据原本只用于判断过程是否可逆,只有对隔离系统中的过程以及大隔离系统中的总过程,熵判据才可用于判断其能否自发。 相似文献
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现代熵理论与《物理化学》教学 总被引:4,自引:0,他引:4
本文扼要介绍了各种熵概念(热力学熵、统计熵、信息熵、物理场熵等)及其应用,鉴于熵理论对现代科学的重要性,提出了在物理化学教学中如何体现的意见. 相似文献
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物理化学尤其是化学热力学公式多、易混淆,学生记忆负担较重。介绍了巧记物理化学中热力学函数关系式和简要分析二元系统固液平衡相图的方法,并以熵变计算为例介绍了物理化学的解题技巧。 相似文献
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动力学、热力学和活化能在花生壳吸附铅离子实验中的应用 总被引:1,自引:0,他引:1
以花生壳为吸附剂、Pb2+为模拟污染物研究了物理化学中固体表面的吸附过程,考察了Pb2+的初始浓度、吸附温度的影响,研究了固体表面吸附反应动力学、热力学和活化能。结果表明:在不同Pb2+初始浓度下,Pb2+在花生壳表面的吸附动力学符合准二级动力学模型,表明该吸附过程是化学吸附为控制步骤的吸附过程。热力学结果表明Pb2+在花生壳表面的吸附是一个自发的放热过程,因为Pb2+由三维运动转变为二维运动导致系统熵减小。活化能Ea=31.35 kJ·mol-1再次证明Pb2+在花生壳表面的吸附是化学吸附过程,这些结果较好地验证了物理化学教学中固体表面的吸附行为。通过该拓展实验加深了学生对固体表面吸附过程的理解,同时,培养了学生的科技创新能力。 相似文献
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Mojtaba Shamsipur Mohsen Irandoust Kamal Alizadeh Vito Lippolis 《Journal of inclusion phenomena and macrocyclic chemistry》2007,59(3-4):203-209
Proton NMR was used to study the complexation reaction of Ag+ with octathia-24-crown-8 (OT24C8) in a number of binary dimethylsulfoxide (DMSO)–nitrobenzene (NB) mixtures at different
temperatures. In all cases, the exchange between free and complexed OT24C8 was fast on the NMR time scale and only a single
population average 1H signal was observed. The formation constants of the resulting 1:1 complexes in different solvent mixtures were determined
by computer fitting of the chemical shift-mole ratio data. There is an inverse relationship between the complex stability
and the amount of DMSO in the solvent mixtures. The enthalpy and entropy values for the complexation reaction were evaluated
from the temperature dependence of formation constants. In all solvent mixtures studied, the resulting complex is enthalpy
stabilized but entropy destabilized. The TΔS° versus ΔH° plot of all thermodynamic data obtained shows a fairly good linear correlation indicating the existence of enthalpy–entropy
compensation in the complexation reaction. 相似文献
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In this work, we discussed the stochastic thermodynamics of mesoscopic electron transfer reactions between ions and electrodes. With a relationship between the reaction rate constant and the electrode potential, we find that the heat dissipation βq equals to the dynamic irreversibility of the reaction system minus an internal entropy change term. The total entropy change Δst is defined as the summation of the system entropy change Δs and the heat dissipation βq such that Δst=Δs+βq. Even though the heat dissipation depends linearly on the electrode potential, the total entropy change is found to satisfy the fluctuation theorem < (e)-Δst>=1, and hence a second law-like inequality reads <Δst>≥0. Our study provides a practical methodology for the stochastic thermodynamics of electrochemical reactions, which may find applications in biochemical and electrochemical reaction systems. 相似文献
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CaMoO4 micro/nano hollow spheres with three different sizes were prepared via a reverse-microemulsion route at room temperature. Through designing a novel thermochemical cycle, the relationship between thermodynamic properties of nano CaMoO4 and bulk CaMoO4 was built. Combined with in situ microcalorimetry, change regularities for the thermodynamic properties of the prepared CaMoO4 micro/nano materials and reaction systems were obtained. The results reveal that size effect has significant influence on thermodynamic properties of micro/nano materials and reaction systems. Along with the size decreasing, the standard molar enthalpy, standard molar Gibbs free energy and standard molar entropy of reaction of micro/nano reaction systems decreased, but the standard molar enthalpy of formation, standard molar Gibbs free energy of formation and standard molar entropy of micro/nano materials increased. 相似文献
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Mohsen Irandoust Mojtaba Shamsipur Hiua Daraei 《Journal of inclusion phenomena and macrocyclic chemistry》2010,66(3-4):365-370
Proton NMR was used to study the complexation reaction of Rb+ ion with 18-crown-6 (18C6) in a number of binary dimethylsulfoxide (DMSO)–nitrobenzene (NB) mixtures at different temperatures. In all cases, the exchange between free and complexed 18C6 was fast on the NMR time scale and only a single population average 1H signal was observed. The formation constants of the resulting 1:1 complexes in different solvent mixtures were determined by computer fitting of the chemical shift mole ratio data. There is an inverse relationship between the complex stability and the amount of DMSO in the solvent mixtures. The enthalpy and entropy values for the complexation reaction were evaluated from the temperature dependence of formation constants. In all solvent mixtures studied, the resulting complex is enthalpy stabilized but entropy destabilized. The ?H° versus T?S° plot of all thermodynamic data obtained shows a fairly good linear correlation indicating the existence of enthalpy–entropy compensation in the complexation reaction. 相似文献
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We study global decay of the bimolecular reaction A+B-->P as c(t) approximately t(-alpha) in a nonlinear transitional flow. A relationship is established between the decay exponent alpha, and a modified Kolmogorov-Sinai entropy, hr. We find that for dynamic conditions which induce relatively strong mixing, the decay exponent is alpha is proportional to ln psi(-Bhr) with B being a characteristic reactive mix-down time for the system, and psi is a space-time scaling parameter. Dynamic conditions which imply weak mixing lead to a degenerate dependence of alpha on hr. The proposed relationship between alpha on hr should be a useful link between the dynamical evolution of the flow field and reaction kinetics in vortex dominated flows. 相似文献
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《The Journal of chemical thermodynamics》2007,39(3):337-343
The binding reactions of the fluoroquinolone with bovine serum albumin (BSA) were investigated by microcalorimetry. The thermodynamic parameters were measured with the help of spectroscopy in a Tris–HCl buffer solution (pH 7.0, made isotonic with sodium chloride) at T = 298 K. Microcalorimetric measurements show that the molar change of enthalpy ΔrHm is insignificant for the reaction, which may suggest that the interaction is governed mainly by entropy, and the interaction between the protein and the drugs is stronger. The results also reveal an entropy–enthalpy compensation relationship of the interaction. 相似文献
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全氟辛基磷酸(C_8F_(17)SO_3H,Perfluorooctanesulfonic acid,POSA)是熔点为90℃的固体超酸.我们首次测得其酸度函数值是-12.11±0.03,并将其用于催化Friedel-Crafts烃基化反应和醇脱水制烯,取得了良好的结果.本文报导我们研究POSA催化酯化反应的动力学和线性自由能关系. 线性自由能关系是研究反应动力学微观过程的有效方法之一.对反应速度常数、平衡常数的测定,对于活化参数△E、△S、△H的计算以及反应机理的深入了解都是非常有用的.近年报导的Wittig反应线性自由能关系的研究即是一例. 我们测定了POSA催化对位取代苯甲酸的乙酯化反应的速率常数k,计算了反应的活化能 相似文献
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Akitomo Tachibana 《International journal of quantum chemistry》1989,35(3):361-372
An “apparatus” operator approach is presented for the extension of the density functional theory of Hohenberg, Kohn, and Mermin. Using the Mermin entropy principle, a one-to-one correspondence is established between the density matrix for the system and the electron charge density for a finite-temperature system in the presence of an apparatus. In the zero-temperature limit in the absence of an apparatus, the Hohenberg–Kohn theory is recovered. The central aspect of this new density functional theory is that the principle of maximum entropy is applied to the system plus its surroundings under the additional constraint that the electron charge density is given. The system is treated as a subsystem of a composite system and is not necessarily in the equilibrium state as in the Mermin theory. As an example, it is shown how, in principle, excited states are encompassed by the theory. 相似文献
19.
Rainer Trültzsch Jörg Beger Hans-Jürgen Buschmann Eckhard Schollmeyer 《Journal of solution chemistry》1994,23(1):53-61
The formation of complexes between crown ethers and acetonitrile, chloroform, and nitromethane were investigated in carbon tetrachloride at 25°C. A significant influence of the ring size on the selectivity of the host is evident. The host 18-crown-6 forms complexes for which the reaction enthalpy and entropy are quite high. Host molecules with benzene side groups form complexes of lower reaction enthalpy and entropy and therefore the complexes formed are less stable than that of the analogous crown ethers without aromatic groups. Solvent effects on the stability constant K, the reaction enthalpy H, and the reaction entropy S were studied for the complexation of malonitrile by 18-crown-6. The reaction enthalpy and entropy values change in accordance with the dielectric constant of the solvent used, but no overall effect on complex stability with change in solvent dielectric constant was observed. 相似文献
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Steric effects of the alkyl groups: evaluation on isolated molecules by means of isodesmic reactions
Several possible scales of steric effects of the alkyl groups were suggested on the basis of isodesmic model reactions, in which a sterically crowded compound is formally synthesized from simpler derivatives. The reaction energies were calculated within the framework of the density functional theory at the level B3LYP/6-311+G(d.p)//B3LYP/6-311+G(d.p) for 6 model systems and 7 various alkyl groups. The most important systems were cis-1,2-dialkylcyclopropanes 1 synthesized from two mono derivatives and sterically crowded derivatives of bicyclo[2.2.2]octane 2 with C(3) symmetry. The scales of steric effects evaluated from the two models were rather different: the first scale depended in effect only on the C atoms in the alpha and beta positions and the effects were almost equal for all primary alkyls. The second scale depended also on the gamma position and the effect of the CH(2)-t-Bu group was much greater than that of the ethyl group. Any relationship between various systems was found rarely, only in the case of very similar reaction series; even in such cases the relationship was sometimes linear, sometimes distinctly curvilinear. It is concluded that any universal scale of steric effects is in principle not possible since these effects depend specifically on the surroundings of the substituent in a particular reaction. Nevertheless, there is a similarity between various scales; a bulky group appears as bulky in any scale. Therefore, very rough correlations of steric effects are possible. 相似文献