多个时间常数线性体系暂态响应方程参数的代数求解法

从线性条件出发, 推导了含n个时间常数体系恒电位阶跃时暂态响应方程, 并提出一套解析形为ΔI=ΔI_∞+sum from i=1 to n k_iexp(-t/τ_i)暂态方程各未知参数的代数解法。该方法可对未知体系时间常数个数进行判定, 比起一般曲线拟合更加快速简便, 且抗干扰能力较强。     

苯酚+环己酮固液平衡的热力学计算

对苯酚+环己酮低温固液平衡体系,直接由相图和基本热力学数据,计算体系热力学性质。使用Gibbs-Duhem方程和四参量GE方程,在220.00～241.00K区间,计算了8个温度的两组元活度系数和GE方程,在241.00K,x2=0.5、GE=783.69J/mol,SE=97.11/(mol.K),HE=24186.69J/mol。241.00K相合熔点化合物的离解平衡ΔrGm=1982.93J/mol,ΔrHm=5753.241J/mol,ΔrSm=15.65J/(mol.K)。体系偏离于规则溶液模型。在化合物存在相区,离解反应的反应焓变和熵变均可视之为常量。液相区不会存在稳定的化合物。     

高氮含能配合物M（ATZ）（bpy）m·nH2O液相生成反应的热动力学

合成了6种固态高氮含能配合物M（ATZ）（bpy）m·nH2O（（1）M=Mn,m=2,n=3;（2）M=Co,m=2,n=7;（3）M=Ni,m=2,n=0;（4）M=Cu,m=1,n=0;（5）M=Pb,m=1,n=3;（6）M=Zn,m=1,n=1;ATZ=5,5′-偶氮四唑,bpy=2,2′-联吡啶）。对它们的结构和性能进行了表征。用RD496-CK2000微热量计测定了298.15 K下各配合物的液相生成反应焓变分别为：ΔrHm^θ（1）=241.245±0.060 kJ/mol,ΔrHm^θ（2）=-256.875±0.050 kJ/mol,ΔrHm^θ（3）=-265.172±0.038 kJ/mol,ΔrHm^θ（4）=-236.538±0.038 kJ/mol,ΔrH^θm（5）=-249.698±0.038 kJ/mol,ΔrHm^θ（6）=-185.072±0.048 kJ/mol。通过试验测定得到的所有液相反应的ΔrHm^θ均为负值,有利于目标物生成;并改变反应温度,研究了它们的液相生成反应的热动力学。改变温度研究了液相生成反应的热动力学,利用反应热化学数据和动力学方程结合热动力学实验数据计算了活化焓（ΔH≠^θ）、活化熵（ΔS≠^θ）、活化自由能（ΔG≠^θ）、表观反应速率常数（k）、表观活化能（E）、指前常数（A）和反应级数（n）。     

中国化学会第21届全国高中学生化学竞赛（决赛）理论试题答案

第1题计算A、B两条直线的斜率:直线A的斜率为-3.76×104直线B的斜率为-1.01×104由Clausius-Clapeyron方程lnp=-ΔvRapTHm C及直线A和直线B的斜率分别得到:ΔHA=84.0kJ.mol-1ΔHB=312.6kJ.mol-1ΔH=ΔHB-ΔHA=312.6kJ.mol-1-84.0kJ.mol-1=229kJ.mol-11-4设xA、xB分别为为DEAA三     

高聚物高压下的状态方程

本文从高分子体系内分子链间相互作用能出发,得到了一个描述高聚物高压下的等温状态方程 从实验中发现n、m为普适常数,n=6.14,m=1,16.在不存在转变的情况下,该方程对处于玻璃态、结晶态及液态高聚物体系均适用.     

微悬臂梁适配子传感器检测维埃克斯、沙林及动力学分析

采用生物素-亲和素法在微悬臂梁传感芯片上固定维埃克斯、沙林适配子,建立了压阻式微悬臂梁适配子传感器检测维埃克斯、沙林及动力学分析方法。传感器对维埃克斯检测的线性范围为2~60μg/L,线性回归方程为ΔUe=0.886C-1.039(n=5,R=0.984,p<0.001),检出限为2μg/L(S/N≥3);对沙林检测的线性范围为10~60μg/L,线性回归方程为ΔUe=0.716C-2.304(n=5,R=0.996,p<0.001),检出限为10μg/L(S/N≥3)。传感器具有良好的选择性和抗干扰能力,对毒剂类似物O-丁基甲基膦酰氯基本无响应。在此基础上,根据受体-配体结合特性与压阻式微悬臂梁传感器输出电压变化之间的关系,建立了传感器检测维埃克斯、沙林的反应动力学模型,根据拟合方程求出的传感器对不同浓度维埃克斯、沙林反应达到平衡时的响应电压(ΔUe)、响应时间(t0)均与实测值非常接近。     

Laplace方程及其推导方法的讨论

当有弯曲表面或界面存在时,在曲面内外便存在由于表面作用而引起的压力差ΔP,其大小可用Laplace方程描述,即ΔP=σ(1/(r_1)+1/(r_2))(1)此方程有许多种推导方法,下面对常见的推导法中的某些问题,作几点粗浅的讨论. 一、对ΔP=σ(dV)/(dV)的推导和理解     

高阻抗电化学体系恒电位脉冲暂态过程研究

提出一套恒电位脉冲测量暂态电流的技术,通过累加生成处理,可大大降低曲线的噪声,再由非等间距的差分处理,可对电化学体系时间常数作出简便的判定,还分析了脉冲幅度以及溶液电阻的作用,并在Fe/H_3BO_3＋Na_2B_4O_7体系和碳钢／砂土体系中对该方法进行了验证。     

强碱性树脂IRA-400对富马酸吸附性能的研究

通过静态吸附试验,研究了强碱性树脂IRA-400对富马酸的吸附性能。结果表明,该树脂与弱碱性树脂IRA-94相比,受pH值影响较小,在pH=3.5时,该树脂对富马酸具有较好的吸附性能,其静态饱和吸附容量为1.466mmol/g湿树脂;该树脂对富马酸的吸附等温线符合Freundlich等温方程,在298.15K,308.15K和318.15K下的相关系数R2均大于0.99,方程的特征参数n1,属"优惠吸附";吸附过程ΔG0,ΔS0,ΔH0,表明此反应过程是放热的,自发进行的,降低温度有利于吸附反应的发生;吸附动力学研究表明,IRA-400树脂对富马酸的吸附过程主要受液膜扩散控制。     

含硅芳二胺固化环氧树脂的反应动力学研究

合成了2种含硅二胺单体3,3'-(1,3-二甲基-1,3-二乙烯基-1,3-二硅氧烷)二苯胺(S1)和4,4'-(1,3-二甲基-1,3-二乙烯基-1,3-二硅氧烷)二苯胺(S2),并对其作为环氧树脂的新型固化剂进行了研究.采用非等温示差扫描量热技术(DSC)研究了其与双酚A型环氧树脂E51体系的固化反应动力学,根据不同升温速率下E51/S1和E51/S2体系的特征温度的变化,分别确定了该两体系的固化反应工艺条件,即:E51/S1体系为100℃/1h+160℃/2h+190℃/3h;E51/S2体系为110℃/1h+170℃/2h+190℃/3h.通过Kissinger方程、Crane方程以及Arrheninus方程对固化反应进行了固化动力学行为研究,得到了两个反应体系的表观活化能ΔE、Arrhenius因子A以及反应级数n等动力学参数.E51/S1体系的ΔE为50.65 k J/mol、A为1.83×105,n为0.87;E51/S2体系的ΔE为51.39 k J/mol,A为1.44×105,n为0.87,由ΔE和A表明,E51和S2的反应活性高于E51和S1的反应活性,即,氨基位于苯环的间位时与环氧基团更容易反应.二者的反应级数相同并且小于1,说明E51与S1和S2之间的反应是复杂反应.在动力学参数的基础上,得到了n级固化动力学模型.     

多个时间常数线性体系恒电量响应的频谱分析

从线性条件出发,利用拉普拉斯变换及其逆运算推导多个时间常数体系在恒电量激励条件下线性响应暂态方程,并推导出恒电量激励下Rs(C₁(R₁(C₂(R₂(C₃R₃)))))电路模型的极化电位响应式. 通过线性响应方程的理论验证以及与实际腐蚀体系的EIS进行对比,结果表明：对恒电量瞬态响应进行频谱分析,可以促进恒电量测量结果与EIS进行更加细致的对比验证. 对含有多时间常数的电极过程,利用阻抗拟合软件进行局部拟合,可以确定初始值的设置,以避免时域的曲线拟合时出现多种结果的局面,大大地提高了恒电量瞬态响应数据解析的准确性.     

Chloride Response of a Cadmium Chloride Electrode

An unsymmetrical quaternary ammonium salt, trinonyloctadecylammonium tetrachlorocadmiate, was used for the preparation of a chloride-selective electrode. The electrode parameters were examined. An equation for the semiquantitative estimation of the electrode response was proposed. The electrode was used for determining chloride ions in blood serum.     

Hydrodynamic voltammetry at channel electrodes: Part VII. Current transients at double channel electrodes

Expressions for the transient current at the downstream electrode in response to galvanostatic electrolysis at the upstream electrode in the channel flow cell were derived by applying double Laplace transformation when the electrode reaction at the upstream electrode is kinetically controlled. The ratio of the transient current to the steady state current or the transient collection efficiency was calculated as a function of electrode geometry and θ

, where U_m is the mean flow velocity in the channel cell, D the diffusion coefficient of the electroactive species, b the half height of the channel, x₁ the length of the upstream electrode and t the time elapsed since the beginning of the galvanostatic electrolysis at the upstream electrode. Curves for the transient collection efficiency can be applied to evaluating the amount of adsorption at the upstream electrode when metal at the electrode is anodically dissolved in solution. Digital simulation was carried out. Transient curves, obtained analytically, were in good agreement with those evaluated from the digital simulation. In order to allow one to draw transient curves readily, we derived a simple approximate equation.     

Effect of enzyme concentration on the dynamic behavior of a membrane-bound enzyme system

The dynamic behavior of the reaction-diffusion system, composed of glucose oxidase (EC 1.1.3.4) immobilized at a uniform concentration in a membrane, used as a glucose electrode is represented by a diffusion equation with a nonlinear reaction-term in one-dimensional space. The mathematical model is analyzed by computer simulation, that is, numerical integration of the equation under various initial and boundary conditions, to examine the effect of enzyme concentration on the response characteristics (responsiveness and linearity in response) of the electrode. The analysis of the responses of the system to stepwise changes in the boundary value (glucose concentration in simple solution) infers that the enzyme concentration governs the patterns of the spatial distributions of the substrates (glucose and dissolved oxygen) in steady states and transient responses. It is also revealed that the response characteristics of the electrode are optimized with concentration of immobilized enzyme and that the system establishes the steady states at the same spatial distributions of the substrates, regardless of the boundary value. The diffusion of the substrates and the oxygen concentration also have significant effects on the response characteristics of the electrode.     

Response mechanism of platinum electrode to uncoupled ions(Ⅰ)——Response of platinum electrode to Pb~(2+),Cd~(2+),Ca~(2+) and Mg~(2+)

The transient response mechanism of the platinum electrode to the uncoupled ions may be interpreted with the mixed phase formation (MPF) model of the transient response of precipitate-based ion-selective electrodes to interfering tons for Kxy<<1 It is discovered that the peak height of the transient signal is related to the solubility of M(OH)2 and hydration heat of M2+ The relation between the positive peak height of transient signal of Pb2+ or Cd2+ and lgaM obey tne Nernst equation,while that of Ca2+ or Mg2+ does not.The equilibrium potential is not of Nernst response for all ions.     

电动势法对LiCl-MgCl2-H2O体系热力学性质的研究

用自制的锂离子选择电极和经典的Ag-AgCl电极, 以电动势法测定了25 ℃时离子强度为0.05—6.0 mol·kg~(-1)范围的LiCl-MgCl_2-H_2O三元体系中LiCl的平均活度系数. 由实验数据, 求出了Pitzer方程、Harned方程和Scatchard方程的参数和系数. 用上述方程计算了LiCl 在该体系中的活度系数, 并与实验值进行比较, 标准偏差小于0.008. 与等压法测定的渗透系数拟合的Pitzer方程参数计算值比较在实验误差范围内. 同时计算了MgCl_2在该体系中的平均活度系数和混合溶液的渗透系数.     

非配对型电极上的示波沉淀滴定

本文研究了非配对型铂电极上的示波沉淀滴定,提出了一种处理电极的新方法即硝酸-王水法,讨论了非配对型电极上示波滴定的机理。     

The kinetics of lithium transport through a composite electrode made of mesocarbon-microbeads heat-treated at 800 °C investigated by current transient analysis

Lithium transport through a mesocarbon-microbeads composite electrode was investigated in a 1 M LiPF₆ solution in ethylene carbonate/diethyl carbonate (1:1 by vol%) using a galvanostatic intermittent titration technique and a potentiostatic current transient technique. From analysis of the anodic current transient it is recognized that when the potential step is small enough for the lithium extraction potential to be below the transition potential, the lithium concentration is not fixed at the electrode surface, but the change in surface concentration with time is determined by the "cell-impedance-controlled" boundary condition. In contrast, when the potential step is large enough for the lithium extraction potential to be above the transition potential, the "real potentiostatic" boundary condition is then established at the electrode surface. Moreover, a "quasi-current plateau" was observed in a certain anodic current transient. This experimental result was theoretically analysed, based upon the modified McNabb-Foster equation as a governing equation. This strongly indicates that the difference in activation energies for lithium deintercalation between the different lithium deintercalation sites existing within the electrode accounts for the different kinetics of lithium transport between the different sites. Electronic Publication     

气体扩散电极高超电位区伏安关系的研究

在气体扩散电极的薄层平板模型基础上, 推演出在高超电位区电位与总表现电流密度呈线性关系的简化式, 直线段的斜率项包含抟质参数和电极结构参数, 调节这些参数可以减小斜率, 从而提高电极的电催化活性, 把简化式应用于氧还原为过氧化氢的反应, 研究氢氧化钾浓度对斜率值的影响, 公式的推论与实验结果相符。