对化学反应速率的实验教学研究

对人教版普通高中教材(必修加选修)中测量化学反应速率的方法进行了改进,将定性实验改进成定量和半定量实验,提出了测量化学反应速率的3种新方法。利用反应物或生成物的性质如生成一定量沉淀所需时间,反应混合物颜色改变所需时间研究了浓度、温度对平均反应速率的影响;对有气体生成的反应,测量反应混合物的质量随时间的减少,或生成气体的体积随时间的增加测量和比较了固体颗粒物大小,催化剂对初始反应速率的影响。     

在“镁与碳酸氢钠溶液反应”实验探究中发展核心素养*

以“镁和碳酸氢钠溶液反应”的实验探究过程为例,针对镁和碳酸氢钠溶液反应比镁和水反应速率快这一现象,运用控制变量法和数字化实验,探究了气体产物成分和使速率加快的原因。凸显学生自主生成的实验探究活动在提升学生科学探究与创新意识、证据推理与模型认知等化学核心素养中的重要作用;归纳了解决实验探究问题的一般思维路径;更好地说明化学是一门以实验为基础的科学。     

氯化氢和氨2种气体的反应的改进

氯化氢和氨气反应时生成氯化铵 ,该反应是一个生成固体且气体体积减小的反应 ,但过去在演示该反应时 ,通常只能看到有白烟 (ＮＨ4 Ｃｌ)生成。笔者对该实验做如下改进后 ,不仅能看到白烟的生成 ,还能感觉到反应的热效应 ;并从实验现象反映出气体体积的减小。　　如图 ,Ａ、Ｂ为 2个三角烧瓶 ,Ａ瓶塞为双孔橡皮塞 ,Ｂ瓶塞为单孔橡皮塞 ,Ａ、Ｂ 2瓶的瓶塞用一根短的粗玻璃管 (10ｍｍ× 80ｍｍ )相连 ,Ａ瓶另一孔插一玻璃导管 ,在瓶内的一端导管紧扎一气球 ,另一端和大气连通。　　操作时 ,先在Ａ、Ｂ 2瓶中分别用向上和向下排空气法收集满氯化…     

活性碳纤维氧化还原过程中气体生成物的研究

本文围绕ACF进行氧化还原反应释出气体的问题采用气相色谱和压力测定等方法对气体的组分、气体释出的规律以及各种影响因素进行了研究,实验结果首次证明了ACF氧化还原反应时生成CO_2气体,其CO_2的释出开始速度较快,随后逐渐减慢,最后达到压力平衡。释出CO_2的反应,表观上与ACF氧化生成羟基和羧基等是平行反应。ACF反应释出CO_2的量随所用氧化剂电极电位上升而增加。但无论何种ACF与何种氧化剂反应,生成CO_2的反应仅是氧化还原历程的一部分。改变ACF的制备工艺或改变ACF氧化还原反应的条件可使CO_2生成的规律改变。体系压力增大,CO_2的释出受到抑制,达到压力平衡后,再放出体系中的气体使之恢复到大气压力时,CO_2释出反应又可继续进行并达到新的压力平衡。     

谈谈卤素单质间置换反应的集约(合)化实验

简单说,集约(合)化实验就是把几个独立的简单实验事实和实验现象归并组合成一个实验.例如,把浓H2SO4跟Na2SO3反应生成的SO2气体,依次通过紫色石蕊液、Ba2水、酸性KMnO4溶液;把电石与水反应生成的C2H2,依次通过CuSO4溶液(洗去H2S)、Br2的CCl4溶液、酸性KMnO4溶液;把KMnO4与浓HCl反应生成的Cl2,依次通过NaBr溶液、KI溶液和KI的淀粉溶液.这些实验组合所产生的集约化效果,历来受到化学教学同仁们的广泛青睐.但是早已流行在教材、参考和教辅资料中的一些不恰当的集约化组合,至今还没有得到足够的重视.     

水中脉冲放电产生H2O2的研究

过氧化氢(H2O2)是强氧化剂,在治理污水中有十分重要的意义,对水中脉冲放电中电压对它的影响进行了研究。结果表明,电压越高,时间越长,H2O2的生成速率减小越快;不同气体成分和流量对H2O2生成也有影响。     

孤岛渣油在分散型催化剂存在下加氢裂化反应动力学的研究Ⅱ．气体生成的动力学

本文研究了孤岛渣油在分散型磷钼酸铵催化剂存在下加氢裂化反应中裂化气体生成的动力学规律。在此基础上，将反应物系分为裂化残渣油、馏分油（Ｃ＿５～４８０℃）、Ｈ＿２Ｓ、甲烷、乙烷、丙烷、丁烷和Ｃ＿２～Ｃ＿４烯烃八个集总，提出了裂化气体生成的一级平行－连串反应动力学网络，进而用随机投点的复合形法求算了气体生成的速率常数和活化能。结果表明，模型计算值与实验数据较为吻合，所提出的气体生成模型对在分散型催化剂存在下孤岛渣油加氢裂化反应中气体的生成反应是合理的。     

品红能否检验SO2

1课题引入教科书在介绍浓硫酸与铜反应时有这样的叙述:浓硫酸与铜在加热时能发生反应,放出能使紫色石蕊试液变红或使品红溶液褪色的气体。从对实验现象的分析中,我们可以得出这样一个结论:浓硫酸与铜反应生成的气体并不是氢气。实验证明,反应生成的气体是二氧化硫[1]。这段话虽     

探究实验中的一个意外发现——镁与碳酸氢钠溶液反应产生大量氢气

学生做实验时偶然发现,表面擦去氧化膜的镁片可与NaHCO3溶液反应产生大量氢气。经过进一步的探究实验,认识到镁片是直接与水反应生成Mg(OH)2和氢气,生成的Mg(OH)2再与NaHCO3反应生成碱式碳酸镁、碳酸钠和水。     

超临界水中甲酸降解过程实验研究

在550℃~650℃,24 MPa~30 MPa,反应停留16 s~46 s的条件下,对初始浓度0.05 mol/L~0.70 mol/L的甲酸溶液在超临界水中的降解过程进行实验研究。结果表明,甲酸降解的气体产物为H2、CO2和CO,其中H2、CO2为主要产物。高温有利于甲酸降解和H2生成。温度较高(600℃)时,压力变化对甲酸降解无明显影响。在一定范围内延长反应时间可提高气体产物中H2的体积分数和碳气化率。甲酸初始浓度对甲酸降解机理有重要影响,浓度较低(0.1 mol/L)时,甲酸降解主要包含脱羧反应和脱羰反应两条反应路径,其中脱羧反应为主反应路径;浓度较高时则有许多副反应发生。碱性添加剂不利于甲酸降解生成H2。     

Intermolecular forces for D2, N2, O2, F2 and CO2

The intermolecular potentials for D₂, N₂, O₂, F₂ and CO₂ are determined on the basis of the second virial coeffincients, the polarizabilities parallel and perpendicular to the molecular axes, and the electric quadrupole moment. The repulsive parts of the potentials are taken from the corresponding Kihara core-potentials. Effects of the octopolar induction are taken into consideration in a unique way. The potential depends on relative orientations of the two molecules as well as the distance r between the molecular centers. This dependence is shown in graphs. A measure of the anisotropy of the potential depth is 0.72 for CO₂ 0.36 for D₂, and smaller than 0.27 for N₂ O₂ and F₂. The remarkable anisotropy for CO₂ and D₂ is due to strong electrostatic quadrupole interactions.     

Ba3 (VO4)2-K2 Ba(MoO4)2 and Pb3 (VO4)2-K2 Pb(MoO4)2 systems

Phase equilibria in the Ba₃(VO₄)₂-K₂Ba(MoO₄)₂ and Pb3(VO₄)₂-K₂Pb(MoO₄)₂ systems have been investigated. In the first system, a continuous series of substitutional solid solutions with the palmierite structure is formed, and in the second one, the polymorphic transition in lead orthovanadate at 100°C restricts the extent of the palmierite-type solid solution to 10–100 mol % K₂Pb(MoO₄)₂. Original Russian Text ? V.D. Zhuravlev, Yu.A. Velikodnyi, A.S. Vinogradova-Zhabrova, A.P. Tyutyunnik, V.G. Zubkov, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 10, pp. 1746–1748.     

The preparation of NbH5(Me2PCH2CH2Me2)2 and NbHL2(Me2PCH2CH2PMe2)2 (L = CO or C2H4)

MMe₅(dmpe) (M = Nb or Ta, dmpe = Me₂PCH₂CH₂PMe₂) reacts with H₂ (500 atm) and dmpe in THF at 60°C to give MH₅(dmpe)_2? NbH₅(dmpe)₂ readily reacts with two mol of CO or ethylene (L) to give NbHL₂(dmpe)₂. The exchange of the hydride ligand with the ethylene protons in NbH(C₂H₄)₂(dmpe)₂ is not rapid on the ¹H NMR time scale (60 MHz) at 95°C.     

配合物[Cu(H2O)(C12H8N2)2].2ClO4的合成、性质及晶体结构

合成了配合物[Cu(H2O)(C12H8N2)2]*2ClO4(C12H8N2为1,10-邻菲咯啉),用元素分析、摩尔电导、红外光谱及电子光谱进行了表征,并测定了配合物的晶体结构.该晶体属单斜晶系,空间群为CC;晶胞参数a=1.9177(2)nm,b=0.81994(0)nm,c=1.62458(14)nm,β=100.104(6)°;V=2.5419(4)nm3,Z=4,F(000)=1300,DC=1.693g/cm3,R=0.0430,wR=0.1195.中心铜(Ⅱ)离子与两个1,10-邻菲咯啉的四个N原子和一个水分子的氧原子配位,形成了一个变形的三角双锥结构.     

Formation of [Cp2TiSbMe2]2, [Cp2TiSb(SiMe3)2]2 and [Cp2TiCl]2·2Mes4Sb2

Reactions of [Cp₂Ti(btmsa)] (btmsa = bis(trimethylsilyl)acetylene) with R₄Sb₂ (R = Me, Me₃Si) give [Cp₂TiSbMe₂]₂ (1) or [Cp₂TiSb(SiMe₃)₂]₂ (2) respectively. [Cp₂TiCl]₂·2Mes₄Sb₂ (3) is serendipitously formed from [Cp₂Ti(btmsa)] and Mes₂SbH containing NH₄Cl traces.     

Conversion of NO in NO/N2, NO/O2/N2, NO/C2H4/N2 and NO/C2H4/O2/N2 Systems by Dielectric Barrier Discharge Plasmas

An experimental study on the conversion of NO in the NO/N₂, NO/O₂/N₂, NO/C₂H₄/N₂ and NO/C₂H₄/O₂/N₂ systems has been carried out using dielectric barrier discharge (DBD) plasmas at atmospheric pressure. In the NO/N₂ system, NO decomposition to N₂ and O₂ is the dominating reaction; NO conversion to NO₂ is less significant. O₂ produced from NO decomposition was detected by an on-line mass spectrometer. With the increase of NO initial concentration, the concentration of O₂ produced decreases at 298 K, but slightly increases at 523 K. In the NO/O₂/N₂ system, NO is mainly oxidized to NO₂, but NO conversion becomes very low at 523 K and over 1.6% of O₂. In the NO/C₂H₄/N₂ system, NO is reduced to N₂ with about the same NO conversion as that in the NO/N₂ system but without NO₂ formation. In the NO/C₂H₄/O₂/N₂ system, the oxidation of NO to NO₂ is dramatically promoted. At 523 K, with the increase of the energy density, NO conversion increases rapidly first, and then almost stabilizes at 93–91% of NO conversion with 61–55% of NO₂ selectivity in the energy density range of 317–550 J L⁻¹. It finally decreases gradually at high energy density. A negligible amount of N₂O is formed in the above four systems. Of the four systems studied, NO conversion and NO₂ selectivity of the NO/C₂H₄/O₂/N₂ system are the highest, and NO/O₂/C₂H₄/N₂ system has the lowest electrical energy consumption per NO molecule converted.     

Phase transitions in Ca3(BN2)2 and Sr3(BN2)2

α-Ca₃(BN₂)₂ crystallizes in the cubic system (space group: ) with one type of calcium ions disordered over of equivalent (8c) positions. An ordered low-temperature phase (β-Ca₃(BN₂)₂) was prepared and found to crystallize in the orthorhombic system (space group: Cmca) with lattice parameters: , , and . Structure refinements on the basis of X-ray powder data have revealed that orthorhombic β-Ca₃(BN₂)₂ corresponds to an ordered super-structure of cubic α-Ca₃(BN₂)₂. The space group Cmca assigned for β-Ca₃(BN₂)₂ is derived from by a group-subgroup relationship.DSC measurements and temperature-dependent in situ X-ray powder diffraction studies showed reversible phase transitions between β- and α-Ca₃(BN₂)₂ with transition temperatures between 215 and 240 °C.The structure Sr₃(BN₂)₂ was reported isotypic with α-Ca₃(BN₂)₂ () with one type of strontium ions being disordered over of equivalent (2c) positions. In addition, a primitive () structure has been reported for Sr₃(BN₂)₂. Phase stability studies on Sr₃(BN₂)₂ revealed a phase transition between a primitive and a body-centred lattice around 820 °C. The experiments showed that both previously published structures are correct and can be assigned as α-Sr₃(BN₂)₂ (, high-temperature phase), and β-Sr₃(BN₂)₂ (, low-temperature phase).A comparison of Ca₃(BN₂)₂ and Sr₃(BN₂)₂ phases reveals that the different types of cation disordering present in both of the cubic α-phases () have a directing influence on the formation of two distinct (orthorhombic and cubic) low-temperature phases.     

Zur Trennung von H2, O2, N2, NO, CO, N2O, CO2, C2H6, C2H4, C2H2, NO2(N2O4) und Feuchtigkeit

Ohne Zusammenfassung     

Synthesis and structural investigation of the compounds containing HF2 anions: Ca(HF2)2, Ba4F4(HF2)(PF6)3 and Pb2F2(HF2)(PF6)

Three new compounds Ca(HF₂)₂, Ba₄F₄(HF₂)(PF₆)₃ and Pb₂F₂(HF₂)(PF₆) were obtained in the system metal(II) fluoride and anhydrous HF (aHF) acidified with excessive PF₅. The obtained polymeric solids are slightly soluble in aHF and they crystallize out of their aHF solutions. Ca(HF₂)₂ was prepared by simply dissolving CaF₂ in a neutral aHF. It represents the second known compound with homoleptic HF environment of the central atom besides Ba(H₃F₄)₂. The compounds Ba₄F₄(HF₂)(PF₆)₃ and Pb₂F₂(HF₂)(PF₆) represent two additional examples of the formation of a polymeric zigzag ladder or ribbon composed of metal cation and fluoride anion (MF⁺)_n besides PbF(AsF₆), the first isolated compound with such zigzag ladder. The obtained new compounds were characterized by X-ray single crystal diffraction method and partly by Raman spectroscopy. Ba₄F₄(HF₂)(PF₆)₃ crystallizes in a triclinic space group P1¯ with a=4.5870(2) Å, b=8.8327(3) Å, c=11.2489(3) Å, α=67.758(9)°, β=84.722(12), γ=78.283(12)°, V=413.00(3) Å³ at 200 K, Z=1 and R=0.0588. Pb₂F₂(HF₂)(PF₆) at 200 K: space group P1¯, a=4.5722(19) Å, b=4.763(2) Å, c=8.818(4) Å, α=86.967(10)°, β=76.774(10)°, γ=83.230(12)°, V=185.55(14) ų, Z=1 and R=0.0937. Pb₂F₂(HF₂)(PF₆) at 293 K: space group P1¯, a=4.586(2) Å, b=4.781(3) Å, c=8.831(5) Å, α=87.106(13)°, β=76.830(13)°, γ=83.531(11)°, V=187.27(18) Å³, Z=1 and R=0.072. Ca(HF₂)₂ crystallizes in an orthorhombic Fddd space group with a=5.5709(6) Å, b=10.1111(9) Å, c=10.5945(10) Å, V=596.77(10) Å³ at 200 K, Z=8 and R=0.028.     

Synthesis and structure of three manganese oxalates: MnC2O4·2H2O, [C4H8(NH2)2][Mn2(C2O4)3] and Mn2(C2O4)(OH)2

Three manganese oxalates have been hydrothermally synthesized, and their structures determined by single-crystal X-ray diffraction. MnC₂O₄·2H₂O (I) is orthorhombic, P2₁2₁2₁, , , , , Z=4, final R, R_w=0.0832, 0.1017 for 561 observed data (I>3σ(I)). The one-dimensional structure consists of chains of oxalate-bridged manganese centers. [C₄H₈(NH₂)₂][Mn₂(C₂O₄)₃] (II) is triclinic, , , , , α=81.489(2)°, β=81.045(2)°, γ=86.076(2)°, , Z=1, final R, R_w=0.0467, 0.0596 for 1773 observed data (I > 3σ (I)). The three-dimensional framework is constructed from seven coordinate manganese and oxalate anions. The material contains extra-framework diprotonated piperazine cations. Mn₂(C₂O₄)(OH)₂ (III) is monoclinic, P2₁/c, , , , β=91.10(3)°, , Z=1, final R₁, wR2=0.0710, 0.1378 for 268 observed data (I>2σ (I)). The structure is also three dimensional, with layers of MnO₆ octahedra pillared by oxalate anions. The hydroxide group is found bonded to three manganese centers resulting in a four coordinate oxygen.