浅谈金属活动性顺序表的应用范围

金属活动性顺序表是按金属在酸性介质中298K时,能形成稳定存在的金属简单离子的标准电极电位（还原电位）由小到大的顺序排列的。     

金属活动性顺序的探讨——由一道初中化学试题引发的思考

列举了金属活动性顺序只能说明反应的趋势,不能说明反应速率的例子。解释了一些常见金属活泼性强,反应速率反而慢的原因。指出并举例说明了一些反应不能用金属活动性顺序来判断反应的方向。总结了在使用金属活动性顺序时应考虑的几点内容。     

中美初中化学教材中金属部分的比较与思考

通过对人教版初中化学教材与美国初中主流科学教育教材《科学探索者》中金属部分进行分析,从内容构成、组织编排、活动设置等几个维度进行比较。旨在为初中化学教材修订及教师对教学内容的二次加工提供建议。     

金属电化学腐蚀的实验探究

金属的电化学腐蚀是高二化学新教材(人教版)“原电池原理及其应用”一节的教学难点,教师按照传统的教学方法向学生讲清楚钢铁在潮湿空气里形成原电池时正、负极发生的反应并不容易。笔者在教学实践中采用实验探究式教学,把课堂教学与研究性学习结合起来,引导学生通过自主活动来探究金属电化学腐蚀的一些规律,既有助于理解、巩固化学知识,又能培养学生的实践能力和探究精神。     

从环境教育视角解析新化学课程标准

本文从环境教育角度对教育部制定的《全日制义务教育化学课程标准(实验稿)》的前言、课程目标、内容标准和实施建议4部分做了分析和讨论。     

关于硝酸与金属反应的计算

硝酸与金属的反应是中学化学中重要的知识点,由此编制的有关计算题变化多端,其命题的思路广、隐蔽性强,解题的灵活性高,对于培养和发展学生的创造性思维能力有很大作用。     

氧化还原反应的知识发展、教材编排与学生学习的融合

论述了氧化还原反应的知识发展顺序、教材编排顺序、学生学习顺序,并据此结合知识类型与认识兴趣理论,就教学中如何将“三序”融合安排提出建议。     

“金属与水反应规律的探究”教学设计及反思

在细致研究课标要求,比较不同版本教材在“金属与水反应”相关内容方面特点的基础上牢牢抓住化学核心知识的逻辑联系,以及核心知识所蕴涵的科学方法和化学思想;同时深入体会学生思维上的特点,并在教学设计中紧紧围绕知识的价值和学生的思维有逻辑地设计3个实验探究活动,着重注意对学生实验设计能力、观察能力、化学思想等方面的培养.     

对化学教学与教材新理念的几点看法

这里所提的科学精神教育问题,主要指对教育科学和化学科学的主要精神的体会,以及在教材中是如何体现的问题。在这里,首先着重提一下科学精神的问题。20世纪不仅有着许多重大的科学技术成就,有些成就,如信息科学与技术的发展,已经深深地影响到整个世界,不但可以使得某些信息在极短的时间内,迅速地传播到世界的每个角落,信息共享的程度与速度也是空前的;     

金属活动性顺序与置换反应

金属活动性顺序是中学化学判断金属元素之间在水溶液中能否发生置换反应的主要依据。     

Solubility and Complexation in the Series of Compounds of Alkaline-Earth and Alkali Metals

The solubility of salts with alkali and alkaline-earth metal cations and its dependence on the anion radius were discussed. The theoretical results were confirmed by experimental data on solubility. The stability of complexes in the Mg²⁺–Ba²⁺ series was considered depending on the ligand charge and radius. The revealed tendencies were explained in terms of the competition between solvent and ligand in solution for a central ion.     

过渡金属络合催化活性顺序的量子化学研究 Ⅰ对烯烃的活化

本文应用以HMO为主简化的量子化学方法研究过渡金属络合活化烯烃分子(以乙烯为例)的催化活性。结果表明过渡金属的催化活性与过渡金属本身的d电子组态和d轨道能级、络合分子的π成键轨道和π~*反键轨道的能级、配位体的电荷性质和空间构型等诸因素有密切的联系。这一结果基本上可以解释过渡金属催化活性顺序、助催化剂及配位体对催化活性的影响等实验规律。     

Supramolecular Functions Related to the Redox Activity of Transition Metals

Abstract

The combination of the properties of different subunits in a multicomponent system may give rise to a function which is defined supramolecular. The presence of transition metals in one or more subunits may induce inter-component processes related to their redox and electron transfer (eT) properties, which trigger the supramolecular function (SF). The following examples are considered: (1) a receptor for transition metals is covalently linked to a fluorescent fragment; following recognition, a metal-to-fluorophore eT process quenches the fluorescence. SF: fluorosensing. (2) an azacyclam macrocycle, hosting the Ni^II/Ni^III redox couple, is covalently linked to a photoactive fragment: the Ni^III state quenches the neighboring fluorophore through an eT mechanism, the Ni^II state does not. SF: redox switching of a fluorescent signal. (3) a Cu^II ion is coordinated by two 2,2′-bipyridine molecules, each bearing a cyclam subunit containing a nickel centre; when nickel is in the divalent state, an inorganic anion X^? (N₃ ^?,NCO^?,NCS^?) is bound to Cu^II; on oxidation, X^? moves to the Ni^III centre. SF: electrochemically triggered translocation of X^? from copper to nickel and vice versa.     

How Absorbed Hydrogen Affects the Catalytic Activity of Transition Metals

Heterogeneous catalysis is commonly governed by surface active sites. Yet, areas just below the surface can also influence catalytic activity, for instance, when fragmentation products of catalytic feeds penetrate into catalysts. In particular, H absorbed below the surface is required for certain hydrogenation reactions on metals. Herein, we show that a sufficient concentration of subsurface hydrogen, H^sub, may either significantly increase or decrease the bond energy and the reactivity of the adsorbed hydrogen, H^ad, depending on the metal. We predict a representative reaction, ethyl hydrogenation, to speed up on Pd and Pt, but to slow down on Ni and Rh in the presence of H^sub, especially on metal nanoparticles. The identified effects of subsurface H on surface reactivity are indispensable for an atomistic understanding of hydrogenation processes on transition metals and interactions of hydrogen with metals in general.     

Diffusion Measurements To Understand Dynamics and Structuring in Solutions Involving a Homologous Series of Ionic Liquids

The self-diffusion coefficients of each of the components in mixtures containing pyridine and each of the homologous series 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imides in acetonitrile were determined using NMR diffusometry (i. e., Pulsed Gradient Spin Echo). The nature of solvation was found to change significantly with the proportion of salt in the mixtures. Increased diffusion coefficients (when corrected for viscosity) for the molecular components were observed with increasing proportion of ionic liquid and with increasing alkyl chain length on the cation. Comparison of the molecular solvents suggests increased interactions in solution of the pyridine with other components of the mixture, consistent with the proposed interactions shown previously to drive changes in reaction kinetics. Discontinuities were seen in the diffusion data for each species in solution across different ionic liquids between the hexyl and octyl derivatives, suggesting a change in the structuring in solution as the alkyl chain on the cation changes and demonstrating the importance of such when considering homologous series.     

一类新型多取代嘌呤类化合物的合成及生物活性

以4-氯-5硝基嘧啶(3)为起始物, 经胺解、还原和环合等反应, 构建了新型的多取代嘌呤-8-硫酮(6)结构. 通过化合物6与卤代物的反应, 获得了该杂环的8位巯基衍生物7a-1~7, 7b-1~5和8, 其结构经元素分析, 1H NMR, IR及MS确证. 生物活性测试结果表明,  化合物6和7具有一定的除草和抗烟草花叶病毒活性.     

State of Platinum Group Metals and Gold in Mineral Acid Solutions and the Catalytic Activity of These Metals in the Oxidation of N-Methyldiphenylamine-4-Sulfonic Acid

The state of rhodium, iridium, platinum, and gold in HCl, HClO₄, H₂SO₄, and HNO₃ solutions was studied by capillary electrophoresis. The electrophoresis was performed in an acidic phosphate buffer solution using an unmodified fused-silica capillary. It was found that the catalytic activity of the metals in the reaction of N-methyldiphenylamine-4-sulfonic acid oxidation with periodates in weakly acidic solutions depends on the analyte speciation. It was found that rhodium and iridium cations formed upon the treatment of a sample with concentrated perchloric acid catalyze the above reaction; this is favorable for the selective determination of these cations in the presence of platinum and gold.