高中教学中如何讲授化学反应的活化能

对比了人教版、苏教版以及鲁科版对化学反应活化能的有关论述。介绍了IUPAC（1996）推荐的活化能的定义,强调了为什么仅有基元反应活化能才有准确的解释（即Tolman的统计观点）,最后提出了在高中阶段如何讲授化学反应活化能的几点建议。     

Arrhenius活化能理论的修正

针对Arrhenius活化能理论的不足,修正了这个理论,建立了一个修正的Arrhenius方程,它能适用于更宽的温度范围。     

化学反应活化能的定义及其与势垒的关系

提出了反应活化能的定义,指出Arrhenius活化能只是其中的一种特殊情况,并阐明了反应活化能与势垒的关系。     

简单碰撞理论的一种推导方法

设想双分子气体反应是由硬球分子先活化、再反应的模式进行,不仅能使简单碰撞理论(SCT)的推导变得更为简便,而且阈能和Arrhenius活化能等概念也变得更加明确。     

溯源辨析“活化分子”概念在化学教材中的角色定位*

“活化分子”作为国内化学教育领域广为人知的科学概念,在各类相关化学教材中都有介绍。然而在国外多种经典化学教材中却完全没有“活化分子”的概念,反映出国内外化学教育领域对化学反应速率理论相关知识点的处理上存在明显的差异与分歧。通过溯源关键历史文献,回顾了“活化分子”概念的形成及其在化学反应速率理论发展过程中的角色演变,指出“活化分子”概念已经退出反应速率理论的舞台,在教材中应更多地呈现其在科学史方面的价值,而不是科学价值。     

对活化能相关问题的探析

在介绍阿仑尼乌斯速率方程基础上,从碰撞理论、过渡态理论和托尔曼统计等视角诠释活化能概念,认为仅以活化能大小作依据判断反应速率大小不严密,并从教学层面和试题角度进行了反思。     

物化实验教材中误差理论的不足

一些国内主要实验教材所编写的误差理论部分存在图象、数值分析和数据处理方面的种种疑问,可予证明。本文提出误差方程和几率误差作为误差计算和误差分析方面的补充。     

有效碰撞理论对促进学生认识发展的价值分析及其教学策略

分析了有效碰撞理论对促进学生能量观、化学反应过程观、微粒观发展的功能与价值,提出了基于单元整体教学设计,以探究方式开展有效碰撞理论教学,将有效碰撞理论的功能与价值显性化的教学策略。     

褐煤模型化合物中含氧官能团脱出反应的理论研究

选取苯甲酸和苯酚作为褐煤含氧官能团模型化合物,采用密度泛函理论(DFT)中的B3LYP泛函和6-311+G(d,p)基组,研究了羧基和羟基可能的脱出反应机理.结果表明,不同含氧官能团脱出方式不同,脱出所需的能量也有差异;含有羧基物质的自催化交联脱羧是相对容易发生的反应;考虑到水分子对含氧官能团脱出的影响,选取甲酸和丙三醇作为褐煤含氧官能团模型,研究了水分子参与反应的过渡态结构及其反应活化能的变化,结果表明,反应中水分子作为质子传递介质能降低反应活化能,加快反应速率,一般1~2个水分子的催化效果较佳;同时研究了Na+,K+及其羧酸盐对丙三醇中羟基脱出反应过渡态结构和反应活化能的影响,表明Na+和K+均能与模型化合物形成络合物,稳定过渡态结构,降低活化能,其中Na+的催化效果更佳;与单纯的离子相比,K+羧酸盐催化效果变化不大,Na+羧酸盐催化能力降低幅度较大.     

关于最弱受约束电子势模型理论中势函数物理意义的讨论

从屏蔽、贯穿和极化作用考虑,对最弱受约束电子势模型理论(简称WBEPM理论)的势函数进行了讨论.通过一系列推导、论证,得出WBEPM理论的有效势的物理意义为:势函数中的第一项表示最弱受约束电子在有效核电荷+Z＇e中心场中的势能;第二项代表最弱受约束电子对非最弱受约束电子和核组成的"实”的极化作用所引起的偶极子场中的势能.     

气相双原子分子自交换电子转移过程中重组能与活化能的相关分析

基于电子转移过程中的基本特征，提出了标度电子转移过程活化能和重组能的两种精确确定方案，并利用有关实验光谱数据拟合的精确势函数对气相双原子分子自交换过程的能量指标进行了确定．分析表明势能面的非谐性修正是重要的，该方案是合理的，所得结果吻合较好，并证明了重组能与活化能并不存在简单的４倍关系．     

Differential Non-Linear Isoconversional Procedure for Evaluating the Activation Energy of Non-Isothermal Reactions

A differential isoconversional non-linear procedure for evaluating activation energy from non-isothermal data is suggested. This procedure was applied to model reactions (simulations) and to the dehydration of CaC₂O₄⋅H₂O. The results were compared with those obtained by other isoconversional methods. This revised version was published online in August 2006 with corrections to the Cover Date.     

Two Types of Uncertainty in the Values of Activation Energy

The activation energies of the same process are often reported to have different values, which are usually explained by the differences in experimental conditions and sample characteristics. In addition to this type of uncertainty, which is associated with the process (ΔE _process) there is an uncertainty related to the method of computation of the activation energy (ΔE _method). For a method that uses fitting single heating rate data to various reaction models, the value of ΔE _method) method is large enough to explain significant differences in the reported values of the activation energy. This uncertainty is significantly reduced by using multiple heating rate isoconversional methods, which may be recommended for obtaining reference values for the activation energy. This revised version was published online in July 2006 with corrections to the Cover Date.     

Mo/MCM-22分子筛碳化钼活性中心结构及甲烷活化机理的密度泛函理论研究

 应用密度泛函理论研究了Mo/MCM-22分子筛上碳化钼活性中心的几何结构和电子结构,以及甲烷在该活性中心上的活化机理. 设计了两种结构的活性中心模型: Mo(CH2)2(模型A)和Mo(CH)CH2(模型B); 它们都嫁接在MCM-22分子筛超笼边缘的T4位的Brnsted-酸性位上,用3T簇模型代替分子筛的骨架,对所设计的模型进行了几何结构优化和电子结构分析. 结构优化结果显示, Mo与CH2端基以双键结合,键长为0.18～0.19 nm, 而Mo与CH端基以叁键结合,键长为0.17 nm. 通过自然键轨道分析,证明中心钼原子以配位键与骨架氧原子结合. 根据前线分子轨道的分析,预测了甲烷活化反应将发生在甲烷分子的HOMO和钼活性中心的LUMO之间,即 C-H 键的电子流向 Mo-C 键的π*轨道. 甲烷 C-H 键发生异裂, H+和H3C-基团分别与 Mo-C 键上的Mo和C成键. 在模型A上,甲烷活化反应的活化能为119.97 kJ/mol; 在模型B上,甲烷的H原子可以分别结合到CH2端基和CH端基上,对应的活化能分别为91.37和79.07 kJ/mol.     

化学反应活化能测定实验

通过测定反应温度和碘化钾浓度对反应速率的影响计算活化能,根据公式推导结果消除了试剂浓度对实验结果的影响。用Origin软件对实验数据进行拟合,从图形中得到反应速率、反应浓度、反应温度和活化能的直观对应关系。改进后的实验由单纯的验证性实验变成了自主设计综合性实验。     

Kinetic Energy Density of the Two-Electron Hookean Atom in Terms of the Ground-State Electron Density

An explicit expression is derived for the kinetic energy density, including the correlation contribution, in terms of the ground-state electron density for the two-electron Hookean atom. This model atom has the merit that while the electrons are tied to an origin by springs, the Coulomb interaction energy between the two electrons is fully incorporated.     

On the Theory of Electrolytic Dissociation,the Greenhouse Effect,and Activation Energy in (Electro)Catalysis: A Tribute to Svante Augustus Arrhenius

Svante Augustus Arrhenius (1859, Vik - 1927, Stockholm) received the Nobel Prize for Chemistry in 1903 “in recognition of the extraordinary services he rendered to the advancement of chemistry by his electrolytic theory of dissociation”. Arrhenius was a physicist, and he received his PhD from the University of Uppsala, where he later became a professor for phyiscal chemistry, the first in the country for this subject. He was offered several positions as professor abroad, but decided to remain in Sweden and to build a Nobel Institute for physical chemistry using the Nobel funds. He remained director of the Institute until his death. There are powerful lessons to take from Svante August Arrhenius’ journey leading to a Nobel laureate as there are from his tremendous contributions to chemistry and science in general, including climate science, immunochemistry and cosmology. The theory of electrolytic dissociation for which Arrhenius received the 1903 Nobel Prize in Chemistry has had a profound impact on our understanding of the chemistry of solutions, chemical reactivity, mechanisms underlying chemical transformations as well as physiological processes. As a tribute to Arrhenius, we present a brief historical perspective and present status of the theory of electrolytic dissociation, its relevance and role to the development of electrochemistry, as well as some perspectives on the possible role of the theory to future advancements in electroanalysis, electrocatalysis and electrochemical energy storage. The review briefly highlights Arrhenius’ contribution to climate science owing to his studies on the potential effects of increased anthropogenic CO₂ emissions on the global climate. These studies were far ahead of their time and revealed a daunting global dilemma, global warming, that we are faced with today. Efforts to abate or reverse CO₂ accumulation constitute one of the most pressing scientific problems of our time, “man's urgent strive to save self from the adverse effects of his self-orchestrated change on the climate”. Finally, we review the application of the Arrhenius equation that correlates reaction rate constants (k) and temperature (T); , in determining reaction barriers in catalysis with a particular focus on recent modifications of the equation to account for reactions exhibiting non-linear Arrhenius behavior with concave curvature due to prevalence of quantum mechanical tunneling, as well as infrequent convexity of Arrhenius plots due to decrease of the microcanonical rate coefficient with energy as observed for some enzyme catalyzed reactions.