关于“阿伏伽德罗常数”的历史考量

从基本物理常数这个视角来看阿伏伽德罗常数会更易理解。最早测出阿伏伽德罗常数的人是法国科学家佩兰。阿伏伽德罗常数的测定历史长达百年,至今仍在继续。"阿伏伽德罗常数"与"物质的量""摩尔"概念具有相同的历史源头,但是在不同学科领域发展着,最后又殊途同归。     

基于手持技术的阿伏伽德罗常数测定

借助手持技术通过电镀法和双液原电池法实验测定阿伏伽德罗常数，进而得出一种新的近似测定阿伏伽德罗常数的方法，并作为教材实验的有益补充，帮助学生理解概念，切实感受化学定量实验的魅力。     

单分子膜法测阿伏伽德罗常数实验中扩散剂的新探索

在单分子膜法测阿伏伽德罗常数实验中,为了克服扩散剂苯毒性大且实验误差大等缺点,通过查阅文献资料,发现环己烷、正己烷的物理性质符合在实验中作扩散剂的要求,并且毒性较苯低,所以选用环己烷、正己烷与苯做对比实验。实验结果表明,用环己烷作扩散剂测得的NA最接近理论值。故在用单分子膜法测阿伏伽德罗常数的实验中,环己烷可以代替苯作扩散剂。既能减小实验误差,又可以降低实验过程中有毒药品对实验者的危害。     

学生园地阿伏伽德罗常数与气体常数测定实验的改进

对阿伏伽德罗常数与气体常数测定实验进行了改进:将原实验中测阴极铜片增重改为测阳极铜片的减重;改变电解液的性质,引入EDTA络合铜离子;用相对更环保的锌片代替铜片等。经过反复实验,最终得到了较优化的实验方案。     

对高考化学试题中部分错误的分析及修改建议

对高考化学试题中出现的小错误,进行了错因分析,并提出了修改建议,其中包括正方形构型的键角,阿伏伽德罗常数的使用,氯化铝的结构,喷泉实验等。     

测定阿伏伽德罗常数的三个里程碑洛喜密脱、爱因斯坦和佩兰

大凡学过化学的人都知道阿伏伽德罗常数N,即1摩尔的任何物质都含有6.02×10~(28)个微粒;在标准状态下,1摩尔的任何气体所占有的体积都约是22.4升.而洛喜密脱(J.J.Loschmidt奥地利)常数是说,在标准状态下,1立方厘米的理想气体含有2.7×     

摩尔新定义和准确测定的阿伏伽德罗常数

针对2019年国际SI单位新标准的实施,依据文献对阿伏伽德罗常数和摩尔物质量原理进行了简短的历史回顾。着重于摩尔新定义的概念和准确测定阿伏伽德罗常数的描述,突出了原子量精密测量技术、纳米量级精密测量技术以及材料制备和表征技术的发展。相对而言,摩尔新定义更能体现科学方法和科学思维同化学知识的关系,将会对无机化学、分析化学、物理化学等课程教学引起巨大的冲击波,并且会波及到每个化学专业本科生。本文内容可为提高本科生的科研思维和科研素质提供借鉴。     

物质的量和摩尔

叙述了两种物质的量的比率的测量方法。介绍了物质的量的SI单位——摩尔。定义了涉及物质的量的一些量,其中包括摩尔质量、一般的摩尔量、阿伏伽德罗常数、摩尔气体常数及法拉第常数等。对物质的量及其单位摩尔的概念作了有关历史的叙述。     

物质的量和摩尔

叙述了两种物质的量的比率的测量方法。介绍了特的量的ＳＩ单位－摩尔。定义了涉及物质的理的一些量，其中包括摩尔质量、一般的摩尔量、阿伏伽德罗常数、摩尔气体常数及法拉第常数等。对物质的量及其单位摩尔的概念作了有关历史的叙述。     

利用视频显微系统及开源软件追踪分析布朗运动

布朗运动理论与实验的结合,有效证实了分子热运动的存在,并可用于布朗粒子扩散系数、尺寸和阿伏伽德罗常数的确定。利用普通显微镜与智能手机实现了布朗运动显微视频的拍摄,用开源的粒子追踪程序追踪布朗颗粒的运动,使得粒子尺寸等物理量的确定非常简便;另外,也为追踪程序创建了用户友好的界面以方便操作。涉及的理论、实验及程序较适合大学生学习,可锻炼他们的动手能力和统计计算能力,并 全面理解布朗运动的概念和随机过程。     

"Alpha"-, "beta"- and "delta"-anhydrodigitoxigenin

The syntheses of 3β-hydroxy-5β-carda-14, 20:22-dienolide (= «β»-anhydro-), 3β-hydroxy-5β-carda-8:14, 20:22-dienolide (= «α»-anhydro-) and «δ»-anhydro-digitoxigenin (= probably 3β-hydroxy-5β, 14β-carda-8, 20:22-dienolide) by the best ways known to date, have been described. «δ»-Anhydro-digitoxigenin represents the thermodynamically most stable isomer. In this isomer the double bond in position 8 is unaffected by hydrogenation with Pt in acetic acid; with perbenzoic acid an epoxide results from which, on hydrogenation, the double bond can be regenerated in its original position. Analogous reactions are known to occur in the 8:14-epoxides.     

化“材”为“筑”

Chemistry is a central, practical and creative discipline. The development of chemistry plays an important role in the progress of science and society, as well as the improvement of the quality of human life. This paper introduces the chemical knowledge of stone, concrete, glass and other inorganic nonmetallic building materials by the anthropomorphically story. Taking nanomaterials as an example, the prospect of building materials development in the future is put forward.     

Making "wheels" and "cubes" from triangles

[Mn(IV)Mn(II)3] triangular units directed by the presence of tripodal alcohols self-assemble in the presence of azide and acetate ligands to form either a [Mn24] "wheel" or a [Mn32] "cube".     

"Turn-on" fluorescent sensing with "reactive" probes

Chemical probes are valuable tools for the investigation of biochemical processes, diagnosis of disease markers, detection of hazardous compounds, and other purposes. Therefore, the development of chemical probes continues to grow through various approaches with different disciplines and design strategies. Fluorescent probes have received much attention because they are sensitive and easy-to-operate, in general. To realize desired selectivity toward a given analyte, the recognition site of a fluorescent probe is designed in such a way to maximize the binding interactions, usually through weak molecular forces such as hydrogen bonding, toward the analyte over other competing ones. In addition to such a supramolecular approach, the development of fluorescent probes that sense analytes through chemical reactions has witnessed its usefulness for achieving high selectivity, in many cases, superior to that obtainable by the supramolecular approach. Creative incorporations of the reactive groups to latent fluorophores have provided novel chemical probes for various analytes. In this feature article, we overview the recent progress in the development of turn-on fluorescent probes that are operating through chemical reactions triggered by target analytes. Various chemical reactions have been implemented in the development of many reactive probes with very high selectivity and sensitivity toward target analytes. A major emphasis has been focused on the type of chemical reactions utilized, with the hope that further explorations can be made with new chemical reactions to develop reactive probes useful for various applications.     

"Clickable" polymersomes

Polymersomes, composed of amphiphilic polystyrene-block-poly(acrylic acid) (PS-b-PAA), with the periphery being covered with azide groups, were used for further functionalization using "click" chemistry.