共查询到20条相似文献,搜索用时 390 毫秒
1.
以镁、铝为电极,以稀NaOH溶液为电解质溶液构成的原电池中,谁是负极?《化学教育》中的“谈谈化学实验设计的创意”(2003年第11期第46页),《中学化学》中的“有关原电池的电极反应式的书写”(2002年第12期第13页),“谈电极反应式书写技能的培养”(2003年第3期第44页)等文章都认为铝是负极。这一结论已得到大部分中学教师的认可,笔者对这一问题专门做了多次实验并查阅许多相关书籍,觉得很有必要对这一观点进行讨论,以飨读者。 相似文献
2.
我们发现 :不少教师授课时 ,对原电池正负极的确定 ,常作“电极名称由电极材料本身的性质决定 ,正极 :材料还原性较弱的极 ,…… ;负极 :材料还原性较强的极 ,……”这种不太确切的论断。许多教学参考书对此也有类似的提法。这对学生学习原电池的知识无疑会造成某些误导和误解。为了便于认识 ,我们先来做两组探究性对比实验 ,利用安培表来检验电流的方向 ,从而判断电子的流动方向 ,确定原电池的正负极。我们知道 :原电池中电子由负极经导线流入正极 ,即电流由正极流向负极 ,而物理电学知识告诉我们 :电流表的指针总是偏向正极 (电流流入的极… 相似文献
3.
4.
石墨负极在Et4NBF4+LiPF6/EC+PC+DMC电解液中的电化学行为 总被引:2,自引:0,他引:2
在PC+EC+DMC复合溶剂体系中,研究了Et4NBF4(四氟硼酸四乙基铵)与LiPF6组成的复合盐电解质对石墨负极材料界面性质的影响.用循环伏安和恒电流充放电测试方法研究了电解液与石墨负极的相容性,通过傅里叶变换红外光谱(FTIR)对固体电解质中间相膜(SEI)的成分变化进行了研究.结果表明,电解液中的Et4NBF4参与了SEI膜的形成;当Et4NBF4浓度为0.2和0.5mol·L-1时,电池首次充放电不可逆容量损失明显减少,循环效率分别七升到76.O%和81.6%.Et4NBF4/LiPF6复合盐电解质改善了PC基电解质与石墨负极的相容性. 相似文献
5.
石墨负极在Et4NBF4+LiPF6/EC+PC+DMC电解液中的电化学行为 总被引:1,自引:1,他引:0
在PC+EC+DMC复合溶剂体系中, 研究了Et4NBF4(四氟硼酸四乙基铵)与LiPF6组成的复合盐电解质对石墨负极材料界面性质的影响. 用循环伏安和恒电流充放电测试方法研究了电解液与石墨负极的相容性, 通过傅里叶变换红外光谱(FTIR)对固体电解质中间相膜(SEI)的成分变化进行了研究. 结果表明, 电解液中的Et4NBF4参与了SEI膜的形成; 当Et4NBF4浓度为0.2 和0.5 mol·L-1时, 电池首次充放电不可逆容量损失明显减少, 循环效率分别上升到76.0%和81.6%. Et4NBF4/LiPF6复合盐电解质改善了PC基电解质与石墨负极的相容性. 相似文献
6.
7.
8.
进行了控制电位、支持电解质种类等条件选择,使得测定背景电流小,标准偏差低于0.2%,并对样品进行了均匀性、稳定性检验,溶液的有效期为二年。 相似文献
9.
引入数字化手持技术设计6个实验,将金属腐蚀速率问题转换为金属腐蚀过程气体产生速率问题,进而转换为一定时间内密闭体系压强变化问题。实验关键是用气压传感器测定一定时间密闭体系气压变化,得到压强-时间曲线,根据曲线斜率分析反应速率,进而解决"金属腐蚀速率"问题。同时,还从"宏观-曲线-微观-符号"四重表征角度深入分析实验,有助于学生深入理解实验过程与反应原理。本实验研究结论是:(1)同一电解质溶液中,电解原理引起的腐蚀速率大于原电池原理引起的腐蚀速率;(2)对同种电解质溶液,在一定浓度范围内,电解质溶液浓度越大,腐蚀越快。 相似文献
10.
11.
12.
C. Kuttenberg E. Scheiber V. Gutmann 《Monatshefte für Chemie / Chemical Monthly》1995,126(8-9):889-895
Summary The influence of the water content on absorption bands in FTIR spectra of monohydric alcohols was studied and the effects were compared to changes in spectra of absolute solvents at various temperatures. The FTIR spectra were recorded by the ATR technique in order to distinguish the weak bands of the solvents from the intensive water bands more easily. By addition of water to anhydrous alcohols both OH stretching and bending bands increased in intensity and width. Similar changes in spectra of anhydrous alcohols can be obtained by decreasing the temperature. Addition of water to monohydric alcohols causes the lengthening of the intramolecular OH bonds to a smaller extent than the shortening of the intermolecular OH bonds. This contraction of the liquid structure is also reflected in other physical and chemical properties.
Eine infrarotspektroskopische Untersuchung über den Einfluß von Wasser auf Alkohole
Zusammenfassung Der Einfluß des Wassergehalts auf die Absorptionsbanden in den FTIR-Spektren einwertiger Alkohole wurde untersucht und die Effekte mit den Veränderungen der Spektren der absoluten Lösungsmittel bei Temperaturvariationen verglichen. Die FTIR-Spektren wurden mit Hilfe der ATR-Technik aufgenommen, um die meist nur schwachen Banden der Lösungsmittel neben den intensiven Wasserbanden besser erkennen zu können. Es zeigte sich, daß durch Zugabe von Wasser zu absoluten Alkoholen sowohl die OH-Streckschwingungs- als auch die Deformationsschwingungsbande an Intensität und Breite zunehmen. Ähnliche Veränderungen der Banden lassen sich auch in den Spektren von absoluten Alkoholen bei Temperaturerniedrigung feststellen. Diese spektroskopischen Veränderungen werden in folgender Weise interpretiert. Die Zugabe von Wasser zu einwertigen Alkoholen bewirkt die Verlängerung der intramolekularen O-H-Bindungen in schwächerem Ausmaß als die Verkürzung der Intermolekularen O...H-Bindungen, d.h. sie bewirkt eine Erhöhung der Symmetrie der H-Brückenbindungen und eine Verstärkung der O...O-Wechselwirkungen. Diese Verdichtung der Flüssigkeitsstruktur spiegelt sich auch in anderen physikalischen und chemischen Eigenschaften wider.相似文献
13.
Yinheng Fan Yunling Zou Dan Jin Qiang Wu Tong Liu Jie Xu 《Frontiers of Chemistry in China》2007,2(4):403-406
A comparison between the initial reaction rates of nanometric and commercial NaH has been studied in four test reactions:
1) hydrogenolysis of chlorobenzene; 2) selective reduction of cinnamaldehyde to cinnamyl alcohol; 3) metallation of dimethyl
sulfoxide; and 4) catalytic hydrogenation of olefins. The experimental results indicate that when NaH is used as a chemical
reagent in the first three reactions, the initial reaction rates of nano-NaH is 230, 120 and 110 times higher than those of
the commercial ones respectively, and it is in agreement with the difference in specific surface areas between these two forms
of NaH. When NaH is used as a catalyst component together with Cp2TiCl2 in the fourth reaction, catalyst with nano-NaH gives extremely high activity in the hydrogenation of olefins, while the one
with commercial NaH gives no activity at all even if a large amount of the commercial NaH is used to make the total surface
area equivalent to that of nano-NaH. Thus, it is evident that although large specific surface area is important for nano-NaH
to be used as a catalyst component, high surface energy with surface defects seems to be more important. The large specific
surface and the activated surface of nano-NaH with high surface energy should be the main factors for their extremely high
chemical reactivity, while whether the former or the latter one plays a leading role depends on the type of reactions involved.
__________
Translated from Chinese Journal of Applied Chemistry, 2007, 24(1): 21–24 [译自: 应用化学] 相似文献
14.
汇总了高分子学科近期的发展情况,介绍了国内高分子部分研究与开发进展,概述了几次学科研讨会所探讨的基本问题。在国家自然科学基金介绍中,着重强调了获资助单位分布广泛性增加、申请数增长偏慢和选题应该更多地关注高分子应用中的基本科学问题,还探讨了国家自然科学基金申请写作注意事项。 相似文献
15.
16.
17.
为解决混合酸(碱)、多元酸(碱)滴定教学中出现的问题,提出一些思路:(1)应在搞清滴定反应及其优先次序前提下,充分利用滴定曲线这一有力工具解决各种问题。(2)教学中,应遵循由易到难、步步深入的原则。在充分讲授单种一元酸滴定的基础上,可按强碱滴混合一元酸、强碱滴多元酸、强碱滴复杂混合酸的顺序安排教学内容。由于规律相似,所以在学生学完强碱滴定酸之后,只需对强酸滴定碱略作介绍即可。另外,提出一种无需复杂计算,仅利用单种一元酸(碱)滴定曲线拼合出复杂酸(碱)体系的近似滴定曲线的新方法,获得的曲线虽不十分精确,但足以给滴定分析可能性判断以及指示剂选择等问题提供有力的支持。 相似文献
18.
A. V. Tvardovskii A. A. Fomkin Yu. I. Tarasevich I. G. Polyakova V. V. Serpinskii I. M. Guseva 《Russian Chemical Bulletin》1992,41(6):987-991
The changes in the thermodynamic functions of the sorbents were calculated for the first time from measurements of the deformations of vermiculite during the sorption of water vapor and adsorption-calorimetric data.Institute of Physical Chemistry, Russian Academy of Sciences, 117915 Moscow. Institute of Colloid Chemistry and the Chemistry of Water, Academy of Sciences of the Ukraine, 252180 Kiev. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1270–1275, June, 1992. 相似文献
19.
On the basis of results of kinetic investigates of many compounds general temperature dependence of Gibbs free energy of activated
complexes created in thermal decomposition processes and the reaction rate constant were calculated.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
Gubkina M. L. Polyakov N. S. Petukhova G. A. Kalmykova O. V. Ustinov E. A. 《Russian Chemical Bulletin》2001,50(4):595-598
The isotherms of water adsorption in the presence of an organic substance vapor with a specified concentration are calculated from experimental data on the joint frontal dynamics of adsorption of water vapor and several organic substances (benzene, hexane, cyclohexane, tetrachloromethane, and perfluorotripropylamine) on two samples of activated carbons. The influence of the organic substances on the equilibrium water adsorption decreases with an increase in the molecule size. 相似文献