氯化铅在水溶液中的熵和焓

标准自由能变化∆G。与∆H。、∆S。的关系是: ∆G。=∆H。-T∆S。(1)只要知道了∆H。和∆S。,便可以计算出不同温度下的∆G。。本实验是通过测量PbCl2溶解度随温度的变化,以作图法计算出∆H。和∆S。。     

信息与服务

O协。N00。闪00。NO仍。门00。价00.州O叭。N00。N00。价00。曰00。仍00。NO叭。N00。NO叭。NON。1O叭。N00。NO口户N00。N00。N00 .2O叭。NO仍。阶O叭。N恤习l四1尺!浑号。补半甥冷坎卜O﹃邢日补牟欢咨比解琴劣卞穴答.’补妞小佘褪众吝︸补牟别滓穴名︸朴牟澎褥尺g︹补习书叹权一09旧哄习。谧补故补半哭长习汉任中成外曰州。066一闪一。一协6一Z一.一66一内一。1661州一。1661刊一.一66一10.16伍一刊︸。1661叫︻.0661州一。1661N一。︻661N工.1661N一。︻661N一。一66︻囚州。1661一0.州66一囚一。工比61一O。叫6小︻州0.问…     

全日制六年制重点中学单课性选修的高中二、三年级化学课本编写提纲(征求意见稿)

原子核。同位素。电子云。电子层和电子亚层。s电子云和p电子云的图象。d电子,f电子。电子的自旋。H到Kr的电子层排布。原子结构与周期系。     

尖晶石对β／β″—Al2O3膜相组成和离子导电性的影响

以wag／P”－AI。O。为固体电解质的CO。、SO。、NO。等气体传感器的研究已有很多报道［‘－‘］，多采用的是个AI。O。结构的电解质。AI刀。和p”－AI刃。的结构具有一定的相似性，但后者具有更高的迁移离子浓度和更开放的晶体结构，表现出更好的离子导电性‘’‘．由于卢”－AI。O。为介稳结构，需要加入如Li。O、MgO等作为稳定剂才能稳定存在．以Li对稳定的产”－al。O。烧结较容易，P”－AI。O。相转化率高，但以MsO为稳定剂制备的”－AI刃。其显微结构和抗吸湿性能更为优越．LJLi对和MgO共同稳定的产”－AI。O。可以…     

Dual-parameter Correlation Analysis of the Fluorescence Data of 1-Methyl-2-formyl-5-substituted Pyrrole(4-nitrophenyl)hydrazones

effect、pohrencct．l－methyl－2－formvl－5－Y－substitutedpyrrole（4－nltrophenyl）Ndrazones．Correlationresultsmrthefluorescencespectraldataofsubstitutedstyrenesanda－Onthebasisof＊themagnitudesofevaluatedlpm。／p、。”］valuesofEq．l，Inwhichp”a“（orPn。。／an，。）andPa（orP。』／a。。）rePresentthePolarandsPin－delocallzatloneffect，wehaverecentlyproposedthattherearefourcategoriesofpossiblecircumstancesforcorrelationanalysisofradlcalreactlvltlesandspectralpropeTtlesl．IBothpolarandsp…     

第二届国家期刊奖科技期刊名单

————3”区Li“川—产队 究所‘”然科学版)-仪阿4”y卜人于2。。。。。中。。。。。。。。。。17 吉霉坤”””’”。。。。。。。中。。。。。。。。。。r。。。。,。中。。。。旧。。。。。。。g”“““g票寞宗羌民’-4。。。华。、。。中。。。中华。。。19。。。。。;2腆-厂 北。机。。。。5 物理学报 中国科学院 中科院物理所20 上海环境科学 上海市 卜海市环保局6 高等学校化学学报 教育部)}林大学、南“大ZI 中国药学杂志 中国科协 中国医学会7 金属学报 中国科协 中国金属学会22 金种铸。及有色合 中国科快 中闷机械工程学《…     

不等式在化学中的应用

中学化学中的数字运算有等式和不等式两种。等式属定式、较具体。呈定向思维;不等式属受式、较抽象。呈发散思维。中学生对化学中的等式运算大多能得心应手。但对不等式的化学意义的建立和求解常感陌生。为此设计不等式的应用。对加强学科间联系。启迪发散思维。提高分析和解决问题的能力。无疑很有必要。本文浅析了不等式在中学化学中的常见应用。     

TiO2-Al2O3作为Mo催化剂担体的研究

Tio。－AI。oa二元氧化物的制备at艺大体可分为两种．一种是利用液相浸渍或气相沉积方法将Tio。担载在AI。0。上，使Tio。主要覆盖在AI。0。表面上［‘－1另一种是通过Ti盐和AI盐混合溶液共沉淀方法使Tio。和AI。0。均匀混合在一起【‘－’1．不同的制备工艺对Tio。－AI。03的表面结构和表面性质有很大影响问．我们曾报导用TICly蒸气化学气相沉积方法制备出了D02在1川2O3表面呈现十分均匀分布的DoZ一周。03复合氧化物担体＊’1．本文进一步考察D0。在周。0。表面的沉积对川。0。孔结构的影响，以及Ti02－A1203作为加氢精制MO催…     

开展微型实验教学之我见

近年来。中学化学实验教学取得了长足进展。但我国地域广阔。发展不平衡。也存在一定问题。     

第26届国际化学奥林匹克竞赛理论试题答案

第２６届国际化学奥林匹克竞赛理论试题答案吴国庆编译（北京师范大学化学系１００８７５）８一＠（ａ）ＨＬ十Ｈ。Ｏ—Ｈ。Ｏ十十Ｌ－Ｋ。。一１．４·１０－‘;Ｃ。。一３．００·回旷’Ｋ。。一［Ｈ。Ｏ”］’／｛Ｃ。。一［Ｈ。Ｏ”」｝（·;Ｃ／Ｋ—３·１０－’／...     

Densities,speeds of sound,excess volumes and viscosities of binary mixtures of mtbe with tetralin and decalin at 303.15 k

Measurements of densities, speeds of sound, excess volumes and viscosities of binary mixture of methyl tert-butyl ether with tetralin and decalin are reported at 303.15?K over the entire range of composition. Excess volumes are measured using batch dilatometer technique. Sound speeds are obtained using ultrasonic interferometer. Densities are computed from excess volume data. Isentropic compressibilities are derived from density and sound speed data. Speeds of sound are evaluated on the basis of Jacobson's free length theory and Schaff's collision factor theory. The predicted values are in good agreement with the experimental results. The viscosity data are analysed on the basis of corresponding states approach. Excess volumes and deviation in isentropic compressibilities are negative and deviation in viscosities are positive over the entire composition range. The experimental results are discussed in terms of possible molecular interactions between unlike molecules.     

Review of Analytical Methods for Atmospheric Oxidants Measurements

Abstract

Instrumental and manual methods currently available for the measurement of atmospheric oxidants are surveyed. Techniques used in the United States are emphasized and their advantages and disadvantages are discussed. Commercial systems are evaluated in terms of general operating principles rather than of specific instruments. The ability of these techniques to meet the measurement requirements defined by U.S. Federal air quality oxidant criteria are discussed. Alternative chemical techniques that may have some advantages over the neutral, buffered KI procedure are discussed. Also some attractive, alternative instrumental procedures that are ozone-specific are presented. These systems are based on chemiluminescence and ultraviolet absorption photometry. Electrochemical and colorimetric methods for total oxidant measurements are compared. Finally, some data are presented on relationships of ozone and total oxidants.     

Some Strategies for the Refinement of Disordered Structures with the SHELXL-97 Refinement Program

1 INTRODUCTION finement stage. The person performing the crysta- llographic manipulations works on numerical data The high degree of order in the arrangement of that are quite different from the diffraction images atoms in a crystal is a fundamental characteristic of on a computer terminal, and most often does not even the crystalline state, an ideal crystal being envisaged see the images. to be constructed of regularly-stacked unit cells, each The refinement program, SHELXL-97[1], has …     

Inorganic electrides

Inorganic electrides are a novel kind of ionic compounds in which the anions are electrons confined in a complex array of cavities or channels and the cations are nanoscale arrays of alkali metal ions that provide charge balance. In electrides the donated electron behaves like a low-density correlated electron gas, whereby the dimensionality of the electron gas and its electronic and magnetic properties are determined by the topology of the cavities in the host matrix. Unlike traditional electrides, in which alkali cations are encapsulated within an organic cage, inorganic electrides are thermally stable. The current inorganic electrides based on alkali metal loaded zeolites can be designed as useful reduced-dimensionality materials. Inorganic electrides are powerful reducing agents, and they are able to reduce small aromatic molecules to the radical anions within the channels of the zeolite.     

钼、钨系过氧化物在Sharpless烯烃环氧化反应中的应用*

钼、钨系过氧化物是非常重要的Sharpless烯烃环氧化催化剂,有着非常广泛的工业发展前景。本文综述了钼、钨系过氧化物的种类,结构,合成方法及催化活性,分析了各种钼、钨系过氧化物的特点以及在催化环氧化领域的发展现状。同时,本文还讨论了钼、钨系过氧化物催化烯烃环氧化反应的机理。评述了在催化环氧化领域中两种主要理论——Mimoun机理与Sharpless机理的争论焦点及发展现状,以及计算化学对两种理论中间过渡态的研究进展,并且重点分析了Sharpless机理的过渡态结构。此外,本文还综述了影响钼、钨系过氧化物催化剂反应活性的各种因素以及质子所产生的副反应。最后,本文对应用于催化环氧化领域的钼、钨系过氧化物未来的研究方向提出了建议。     

Contactless conductivity detection for microfluidics: designs and applications

Different methods for construction of contactless conductivity detectors (CCD) for microchip electrophoresis device are described in this review. This includes three main schemes of CCD for microchips, such as (i) the detection electrodes are placed along the microchannel from outside of the microchip and they are insulated from the channel by the cover lid of microchip device; (ii) the electrodes are placed across of the microchannel in the same plane and they are insulated by thin separation channel walls and (iii) electrodes are buried in widened part of microchannel and they are insulated from solution by ultrathin layer of silicon carbide. Specific issues related to the CCD on microfluidics are discussed, such as an influence of shape and magnitude of ac voltage and placement of electrodes and their insulation. Various applications for security, pharmacological, bioassays and food analysis purposes are described.     

异丙醇的O-H伸缩振动泛频光谱和分子构像

使用高灵敏的光腔衰荡光谱(CavityRingDownSpectroscopy)技术测出了异丙醇的O-H伸缩v=4、5振动泛频光谱,每个振动能级都有三个吸收峰,被归属为分子构像的O-H伸缩泛频吸收.给出了光腔衰荡光谱的振动泛频吸收的谱带强度公式,并求得分子不同构像在不同振动能级的O-H伸缩泛频吸收的谱带强度;同时利用局域模理论,求得分子各O-H伸缩局域模振子的机械频率(X1)、非谐性(X2)以及解离能(D).用密度泛函(DFT)B3LYP/6-31+G*理论方法优化了分子的各种可能构像,验证了分子存在反式(trans)和偏转(gauche)两种稳定构像,计算的分子的O-H伸缩频率及构像稳定性同实验结果是一致的.     

Synthesis,Redox and Spectroscopic Properties of Pterin of Molybdenum Cofactors

Pterins are bicyclic heterocycles that are found widely across Nature and are involved in a variety of biological functions. Notably, pterins are found at the core of molybdenum cofactor (Moco) containing enzymes in the molybdopterin (MPT) ligand that coordinates molybdenum and facilitates cofactor activity. Pterins are diverse and can be widely functionalized to tune their properties. Herein, the general methods of synthesis, redox and spectroscopic properties of pterin are discussed to provide more insight into pterin chemistry and their importance to biological systems.     

The Application of NMR Spectroscopy and Chemometrics in Authentication of Spices

Spices and herbs are among the most commonly adulterated food types. This is because spices are widely used to process food. Spices not only enhance the flavor and taste of food, but they are also sources of numerous bioactive compounds that are significantly beneficial for health. The healing effects of spices are connected with their antimicrobial, anti-inflammatory and carminative properties. However, regular consumption of adulterated spices may cause fatal damage to our system because adulterants in most cases are unhealthy. For that reason, the appropriate analytical methods are necessary for quality assurance and to ensure the authenticity of spices. Spectroscopic methods are gaining interest as they are fast, require little or no sample preparation, and provide rich structural information. This review provides an overview of the application of NMR spectroscopy combined with chemometric analysis to determine the quality and adulteration of spices.