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氧化还原反应是大学普通化学课程中的一个重点。某些普通化学教科书在叙述这部分内容时,还存在着一些值得商榷的问题。下面结合实验讨论其中的几个问题。一、氧化还原反应是可逆反应氧化还原平衡是四大平衡之一,但却很少讨论氧化还原反应的可逆性。下面的实验可以说明氧化还原反应可逆性这个问题。 相似文献
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以“设计过氧化氢使用注意事项标签”为项目主题,开展高中化学“氧化还原反应的应用”教学。学生通过说明书对比发现问题,完成“探究过氧化氢能否与氧化性物质混用”“探究过氧化氢为何不能与还原性物质混用”“探究过氧化氢起消毒作用原理”等3个主项目任务及“寻找日常生活中常见消毒剂”的拓展任务,完成过氧化氢性质的预测及验证,在探究过程中建构并应用价性模型,形成从化合价角度认识物质氧化性或还原性的思路方法,认识氧化还原反应的重要意义。本教学设计为单课时微项目,学生思维的开放度稍弱,可以适当延长课时。 相似文献
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采用准实验研究设计,选择高一年级2个班的学生作为实验对象,对实验组学生进行教学干预,让他们采用解释驱动探究学习电解质和氧化还原反应概念,控制组学生按照学校正常教学安排进行。结果显示实验组学生的概念理解高于控制组,并且对氧化还原反应概念的理解呈现显著性差异。解释驱动探究有效促进了学生对科学概念的理解和迁移,并消除了相异构想。 相似文献
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本文对如下几个问题作一些讨论:(1)氧化还原反应的速度和其电位差ΔΦ值的大小无关;(2)反应活化能;(3)对氧化还原反应机理作一粗略介绍。一、氧化还原反应的速度和ΔΦ值无关氧化还原反应不像酸碱反应那样可在瞬间完成。氧化还原反应进行的速度很不相同,有的进行的较快,许多氧化还原反应进行得很慢。两个半反应的电位Φ的差值,可预测所给的 相似文献
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掺杂SrTiO3体系上甲烷氧化偶联反应的研究—活性氧物种的作用 总被引:1,自引:0,他引:1
本文采用循环氧化还原法,脉冲反应及TPD等实验手段对钙钛矿型氧化物掺杂SrTiO_3体系上甲烷氧化偶联反应中的活性氧物种的作用进行了研究.结果表明,催化剂由于掺杂产生的未被充分还原的氧物种(O~(α-)(0<α<2)是活化甲烷并促使其发生偶联反应的主要的活性中心,而表面晶格氧(O_L~(2-))则主要使甲烷深度氧化;消耗掉的未被充分还原的氧或晶格氧可以在高温下氧气氛中氧化复原.对于掺杂的SrTiO_3样品,体相中的氧在惰性气氛或还原气氛中可以向表面扩散.吸附氧可能不直接与甲烷作用而主要通过催化剂表面活性氧物种(O~(α-)或O_L~(2-))而起作用. 相似文献
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为了在基础教学实验中引入绿色化学理念以及强化氧化还原反应操作,本文设计了苯甲醛和安息香的相互转化实验:以苯甲醛为原料经维生素B1催化得到安息香,再用硼氢化钠还原安息香得到二苯乙二醇,二苯乙二醇用新型绿色催化剂NaMnOx氧化回到苯甲醛。通过氢核磁共振(1H NMR)对氧化还原反应的产物结构进行了鉴定,液相色谱分析结果表明氧化反应转化率达到90%以上。通过这一循环转化反应的实现,一方面树立了学生的绿色化学理念,另一方面加强了氧化及还原反应的操作训练,在进一步锻炼学生实验能力的同时,使其对化学反应的认知与评价更加完整。 相似文献
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V. H. Martínez-Landeros Bruce E. Gnade M. A. Quevedo-López R. Ramírez-Bon 《Journal of Sol-Gel Science and Technology》2011,59(2):345-351
In this work we report the performance of permeation barriers based on organic/inorganic multilayer stacks. We have used PMMA-SiO2 (poly methyl methacrylate-silica) hybrid films synthesized through a sol–gel route as organic–inorganic components, whereas
Al2O3 thin films were used as the inorganic component. The hybrid layers were deposited by dip coating and the Al2O3 by atomic layer deposition (ALD), films were prepared on polyethylene naphthalene (PEN) substrates. The permeability of the
films and stacks is evaluated using helium as the diffusion gas in a custom made ultra-high vacuum system. The results show
that permeability for PEN is reduced from 5 × 10−3 g/m2-day to about 9 × 10−5 g/m2-day for the best multiple barrier evaluated. Increased barrier properties are due to the increasing in the path and hence
the lag-time of the permeating gas. In particular, we report the surface roughness of the different layers and its impact
on the barrier performance. The hybrid layers reduced notably the roughness of the bare PEN substrate improving the quality
of the Al2O3 layer in the barrier. The optical transmittance of the barriers in the visible region is higher than 80% in all the studied
cases. 相似文献
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R. Amadelli A. De Battisti L. Doubova A. B. Velichenko 《Russian Journal of Electrochemistry》2008,44(1):131-137
An electrochemical kinetic investigation of nitrite oxidation to nitrate on RuO2 is discussed. The process is studied by cyclic voltammetry, steady-state measurements and potential step measurements. The
overall oxidation reaction is a two-electron process where the first step involves a reversible charge transfer: NO2− ⇔ NO2 + e− The one-electron oxidation of nitrite yields adsorbed NO2 which is further oxidized to adsorbed (NO2)+ and subsequently desorbed via a chemical reaction. In the general case, fit of experimental data is obtained with adsorption
described by a Temkin isotherm unless the electrode is pre-treated at a cathodic potential where the (NO2)ads is removed. This treatment lowers the degree of coverage by intermediates but not the nature of the slow step.
Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 1, pp. 142–149.
The text was submitted by the authors in English. 相似文献
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S. A. Mitchenko T. V. Krasnyakova I. V. Zhikharev 《Theoretical and Experimental Chemistry》2008,44(5):316-319
We report the catalysis of the hydrochlorination of acetylene on the surface of dry K2PdCl4 subjected to prior mechanical activation in an atmosphere of acetylene or propylene. The stereochemistry of the reaction
corresponds to trans addition of the halogen and hydrogen atoms to the C-C triple bond. The hydrogen halide is the source
of the halogen atom in the reaction product. The mechanical activation of K2PdCl4, in contrast to the case of K2PtCl4, is also capable of activating the C-C double bond: propylene is hydrochlorinated under similar conditions to isopropyl chloride.
Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 5, pp. 306–309, September–October, 2008. 相似文献
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血橙因果肉颜色呈血红色而得名,血橙果肉的颜色深浅取决于花色苷的含量。该含量容易受温度、光照、空气湿度、pH等因素影响而发生变化。从果肉“红色”的形成、“红色”的深浅程度、血橙对人体健康的影响等3个方面对血橙的“红色”进行探讨,以期为读者科普血橙中蕴含的化学知识,感受化学与生活的紧密联系。 相似文献
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T. V. Mironyuk V. L. Struzhko S. N. Orlik 《Theoretical and Experimental Chemistry》2007,43(4):255-260
A series of cobalt-containing granulated and structured catalysts based on zirconium and aluminum oxides has been studied.
The optimum composition of binary oxide samples (80% ZrO2 − 20% Al2O3) for the selective reduction of nitrogen monoxide with methane (84% conversion of NO achieved at 320 °C) has been determined.
The activity of the structured catalysts depends on both the composition of the secondary carrier (ZrO2, Al2O3, and their mixture) and on the nature of the skeleton of the cellular structure (cordierite, kaolin-aerosil).
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Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 4, pp. 237–241, July–August, 2007. 相似文献
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Methyl palmitate (I), methyl stearate (II), stigmasterol (III), β-sitosterol (IV), (O -acyl)-β-D -glucopyranosyl-(1→3)-stigmasterol (V), (O -acyl)-β-D -glucopyranosyl-(1→3)-β-sitosterol (VI), β-D -glucopyranosyl-(1→3)-stigmasterol (VII), β-D -glucopyranosyl-(1→3)-β-sitosterol (VIII), β-D -ecdysone (IX), diosgenin-3-α-L -rhamopyranosyl-(1→2)-[α-L -arabinofuranosyl-(1→4)]-β-D -glucopyranoside (X), diosgenin-3-O -β-chacotrioside (dioscin) (XI), and diosgenin-3-O -α-L -rhamnopyranosyl-(1→4)-α-L -rhamnopyranosyl-(1→4)-[α-L -rhamnopyranosyl-(1→2)]-β-D -glucopyranoside (XII) were isolated and characterized from the stems of Paris formosana Hayata (Liliaceae). 相似文献
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A. Sakunthala M. V. Reddy S. Selvasekarapandian B. V. R. Chowdari H. Nithya P. Chirstopher Selvin 《Journal of Solid State Electrochemistry》2010,14(10):1847-1854
The compound, lithium trivanadate (LiV3O8), was synthesized by the polymer precursor method, using the polymer polyvinylpyrrolidone. The electrochemical performance
of LiV3O8 was compared with LiV3O8 synthesized by the solid state reaction method. The prepared compounds were characterized by X-ray diffraction, scanning
electron microscopy, and high-resolution transmission electron microscopy techniques. The electrochemical performances were
studied by cyclic voltammetry and galvanostatic cycling in the voltage range of 2.0 to 4.0 V at room temperature (25 °C).
The compound prepared by the polymer precursor method was found to have a good cycling stability. A reversible capacity value
of 203 mAh/g (2.18 mol of Li) and 170 mAh/g (1.83 mol of Li) was obtained at the end of the 70th cycle, at a current density
of 30 and 120 mA/g, respectively. 相似文献