电解水演示实验的探究

电解水实验为中学化学的一个经典演示实验,然而在实验中很难得到氢气和氧气的体积比为2∶1的结果。文章从离子电迁移率、超电势、溶液的酸碱度等影响电解水反应的主要因素入手,研究了电解水实验的科学原理,并运用这些原理结合改进后的实验装置进行了电解水实验过程的探究,获得了电解水实验的满意效果,很适合在课堂中进行演示。     

通过实验探究激发和培养学生的创造力

以课本中的电解水实验和草酸与高锰酸钾反应的实验为基础,同时基于碱式碳酸铜与甲酸反应实验中遇到的实际问题,设置科学问题,开展实验探究,重视实验探究的过程,让学生体验通过科学研究解决科学问题的全过程,激发学生的潜质,培养学生的创造力。     

利用手持技术探究石墨电极电解水的实验

石墨电极是中学电化学实验中常用的一种惰性电极,但其在电解水实验中造成氧气体积偏小和石墨阳极更易损耗的原因目前还不清楚。利用手持技术探究石墨电极电解水的实验,并深入研究造成偏差的原因。实验结果表明石墨电极对氢气吸附能力大于氧气,阳极电解产生的自由基与石墨反应是造成气体体积偏差和阳极损耗的主要原因。     

电解水中电极材料与电解条件的选择

义务教育初中化学电解水的实验（实验3～1）是为了给学生学习水的组成提供感性认识。因此,做好该演示实验,特别是使实验结果接近H2和Q2的体积比为2：1的理论值,成为讲好这节课的关键。本文从分析实验结果产生误差的原因及减少误差所采取的措施出发,通过自制的电解水装置,选择容易找到的电极材料及与之相匹配的电解质及溶液浓度、电压等条件的对比实验结果说明使实验结果更接近理论值的条件,为做好本实验提供参考。一、电解水时氢氧体积比产生误差的原因电解水的化学原理是：阴极：2H+＋22—HZ十阳极：4OH－－4e、ZH。O＋OZt“”…     

电解水演示实验的创新设计

设计了一个全新的电解水演示实验,将太阳能电池、电解水制氢、氢氧燃料电池一体化构成一个整体的演示实验,可以帮助学生系统了解与氢相关联的储能用能技术和基于氢的洁净能源的开发和应用,激发学生利用化学知识服务于国家绿色发展理念的使命担当。     

发挥知识教育功能 提升学生核心素养——以“水的组成”为例

以“水的组成”一课为例,通过空瓶魔术揭秘、电解水探究、化学式推导等活动,阐述教学过程中如何发挥知识的教育功能及对提升学生核心素养的贡献。     

非贵金属催化剂的合成及其电解水制氢——推荐一个综合化学实验

介绍一个电解水制氢催化剂的合成、物性表征及其性能评价的综合实验。本实验采用水热法和湿化学法制备了Cu-MoS₂/CNTs电催化剂,之后应用伏安法和交流阻抗技术评价了催化剂的性能,以巩固学生对于不可逆电极和超电势概念的理解和学习。本实验通过合成和筛选最佳组分的电催化剂,有助于激发学生的科研兴趣和提高学生综合实验能力。     

“电解——利用原电池产生的电流电解硫酸钠溶液”实验的商讨与改进——“无机化学实验”试用教材探讨之二

本实验按“教材”提供的实验步骤我们已在79届学生实验中做过一次,由于我们水平不高,只是粗略在观察到在电解槽的阴极上出现使酚酞变红色的现象,并未进一步观察证明两极上产生氢气和氧气的气泡。但在对电解原理上却是作为电解水的本质来理解的,即硫酸钠在溶液中实际只起电流传递作用。     

外场强化电解水析氢

电解水析氢过程中的能量消耗及析氢效率有很多影响因素,其中,电荷转移电阻和催化剂表面气泡覆盖率是最为重要的两个因素。研究发现,在电解水析氢过程中利用外场进行强化,可以有效减小电荷转移电阻和催化剂表面气泡覆盖率,如温度场能为反应过程中电荷的转移注入能量,从而降低电荷转移电阻,降低过电位;而电场能直接调整催化剂电子结构或诱导电解液离子重新分布,从而促进界面电荷转移;光场则可以诱导水分子极化,增大剩余电场,同时拉伸水分子中氢键,有利于水分解产生氢气和氧气。因此,在电解池中引入温度场、磁场、超声场、电场、超重力场和光场等外场也是降低能耗、提高析氢效率的有效策略。近年来,关于外场强化电解水的研究工作虽有报道,但研究偏少且未见系统性的归纳总结。本文即综述了近年来在电解水析氢过程中利用外场强化的研究进展。介绍各种外场强化电解水析氢的基本原理,同时通过实验案例分析各外场手段的效果,并总结外场强化电解水析氢面临的挑战及发展方向。     

自支撑电极材料的制备及其电解水性能实验设计

介绍了创新型新能源实验“自支撑电极材料的制备及其电解水性能实验设计”的开设,阐述了由科研成果到开设实验教学的基本设计思路,详细说明了自支撑非铂催化电极的制备方法、结构表征及其在全解水中的应用,并总结分析了该实验课程实践后的经验与反思。教学实践表明：学生对新能源实验表现出了高度的兴趣;实验的开展在培养学生独立调研、实验和写作能力的基础上,更增强了其创新思维和逆向思维的能力。     

Physicochemical foundations of synthesis of new ferromagnets from chalcopyrites A<Superscript>II</Superscript>B<Superscript>IV</Superscript>C<Stack><Subscript>2</Subscript><Superscript>V</Superscript></Stack>

The results of studying phase equilibria of ternary A^IIB^IVC^V systems have been reported. Physicochemical foundations have been developed for the synthesis of new ferromagnets with Curie temperatures above room temperature structurally compatible with basic semiconducting materials. Methods of synthesis and physicochemical properties of manganese-doped A^IIB^IVC₂^V ferromagnets have been described. The results of theoretical simulation of magnetic properties have been considered and basic approaches to the explanation of the emergence of ferromagnetism in A^IIB^IVC₂^V doped with 3d metals have been surveyed. The most promising ways to produce and study dilute magnetic semiconductors as spintronics materials have been presented.     

Determination of the enthalpy of fusion of K<Subscript>3</Subscript>TaO<Subscript>2</Subscript>F<Subscript>4</Subscript> and KTaF<Subscript>6</Subscript>

Areas of fusion and crystallization peaks of K₃TaO₂F₄ and KTaF₆ were measured using the DSC mode of a high-temperature calorimeter (SETARAM 1800 K). On the basis of these quantities, considering the temperature dependence of the calorimeter sensitivity, values of the fusion enthalpy of K₃TaO₂F₄ at the fusion temperature of 1181 K of (43 ± 4) kJ mol⁻¹ and of KTaF₆ at the fusion temperature of 760 K of (8 ± 1) kJ mol⁻¹ were determined.     

Determination of the enthalpy of fusion of K<Subscript>3</Subscript>NbO<Subscript>2</Subscript>F<Subscript>4</Subscript>

Areas of fusion and crystallization peaks of K₃NbO₂F₄ were measured using the DCS mode of a high-temperature calorimeter (SETARAM 1800 K). On the basis of these quantities, considering the temperature dependence of the calorimeter sensitivity, the value of the fusion enthalpy of K₃NbO₂F₄ of (98 ± 6) kJ mol⁻¹ was determined at the fusion temperature of 1257 K.     

Coefficients of thermal expansion of KPb<Subscript>2</Subscript>Cl<Subscript>5</Subscript> and RbPb<Subscript>2</Subscript>Br<Subscript>5</Subscript> crystals

The temperature dependence of unit cell parameters for monoclinic KPb₂Cl₅ and tetragonal RbPb₂Br₅ crystals was studied in the range of 100–298 K. Linear and volume thermal expansion coefficients were determined.     

Effect of SO<Subscript>2</Subscript> on chlorination of Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> + Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> mixtures

The reaction of Bi₂O₃ + Fe₂O₃ mixtures with chlorine and SO₂ at 250–700°C is studied. At 300–500°C, the degree of bismuth chloride sublimation from the oxide mixture increases in the presence of SO₂. Chemical sublimation of FeCl₃ occurs after BiCl₃ is virtually completely recovered from the solid phase.     

2,4‐Di­nitro­phenyl­hydrazones of 2,4‐di­hydroxy­benz­aldehyde, 2,4‐di­hydroxy­aceto­phenone and 2,4‐di­hydroxy­benzo­phenone

In 2,4‐di­hydroxy­benz­aldehyde 2,4‐di­nitro­phenyl­hydrazone N,N‐di­methyl­form­amide solvate {or 4‐[(2,4‐di­nitro­phenyl)­hydrazono­methyl]­benzene‐1,3‐diol N,N‐di­methyl­form­amide solvate}, C₁₃H₁₀N₄O₆·C₃H₇NO, (X), 2,4‐di­hydroxy­aceto­phenone 2,4‐di­nitro­phenyl­hydrazone N,N‐di­methyl­form­am­ide solvate (or 4‐{1‐[(2,4‐di­nitro­phenyl)hydrazono]ethyl}benzene‐1,3‐diol N,N‐di­methyl­form­amide solvate), C₁₄H₁₂N₄O₆·C₃H₇NO, (XI), and 2,4‐di­hydroxy­benzo­phenone 2,4‐di­nitro­phenyl­hydrazone N,N‐di­methyl­acet­amide solvate (or 4‐­{[(2,4‐di­nitro­phenyl)hydrazono]phenyl­methyl}benzene‐1,3‐diol N,N‐di­methyl­acet­amide solvate), C₁₉H₁₄N₄O₆·C₄H₉NO, (XII), the molecules all lack a center of symmetry, crystallize in centrosymmetric space groups and have been observed to exhibit non‐linear optical activity. In each case, the hydrazone skeleton is fairly planar, facilitated by the presence of two intramolecular hydrogen bonds and some partial N—N double‐bond character. Each molecule is hydrogen bonded to one solvent mol­ecule.     

Structure of Zn<Subscript>3</Subscript>P<Subscript>2</Subscript>

The structure of Z_n3P₂ (P 4₂/nmc, a = b = 8. 0785 Å, c = 11. 3966 Å) was solved and refined to R = 3. 2% in a precision X-ray diffraction experiment (λ-MoK _a, graphite monochromator on a primary beam, 27,496 reflections) . Interatomic distances and bond angles have been determined. The fcc lattice of the structure is built from phosphorus atoms, and the zinc atoms occupy 3/4 of all tetrahedral voids; the structure is described by two equivalent models where 1/4 occupied (by zinc atoms) and 1/4 vacant voids change places. The zinc atoms that occupy the voids following the diamond principle do not change places.Original Russian Text Copyright © 2004 by I. E. Zanin, K. B. Aleinikova, M. M. Afanasiev, and M. Yu. Antipin__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 889–892, September–October, 2004.     

Influences of <em>Dryopteris crassirhizoma</em> Extract on<em> </em>the Viability, Growth and Virulence Properties of <em>Streptococcus </em><em>m</em><em>utans</em><em></em>

Dryopteris crassirhizoma is traditionally used as an herbal remedy for various diseases, and has been identified in a previous study as a potential anti-caries agent. In this study, the effect of a methanol extract of D. crassirhizoma on the viability, growth and virulence properties of Streptococcus mutans, a cariogenic dental pathogen, was investigated. In addition, the phytochemical composition of the extract was analyzed. The extract showed bactericidal and bacteriostatic activity against oral bacteria (MIC and MBC of S. mutans: 62.5 and 250 μg/mL, respectively). At two times the MBC, the extract significantly eliminated S. mutans up to 99.9% after 1 h incubation. The extract also dose-dependently reduced growth rates of S. mutans at sub-MIC levels. Furthermore, at sub-MIC levels, virulence properties (acid production, acid tolerance, glucosyltransferase activity and sucrose-dependent adherence) of S. mutans were also inhibited in a dose-dependent manner. GC-MS analysis revealed the presence of mono and disaccharides (44.9%), fatty acids (12.3%) and sugar alcohols (6.8%) in the extract. These data indicate that the extract might be useful for the control of dental caries.     

Mechanism and kinetics of formation of La<Subscript>2</Subscript>SrFe<Subscript>2</Subscript>O<Subscript>7</Subscript> and Nb<Subscript>2</Subscript>SrFe<Subscript>2</Subscript>O<Subscript>7</Subscript>

Phase formation processes in the systems Ln₂O₃-SrO-Fe₂O₃ (Ln = La, Nd) in air in the temperature range 1200–1500°C were studied. The synthesis of the complex ferrites La₂SrFe₂O₇ and Nb₂SrFe₂O₇ involves the formation of the intermediate compounds LnFeO₃ and LnSrFeO₄ and occurs by the same mechanism as the synthesis of the corresponding aluminates, but much faster.