This paper presents a discussion on using the distribution diagram to derive the titration curve concerning monoprotic acid.
In physical chemistry, transition state theory is the key and difficult point of chemical kinetics. In this work, three methods of computational chemistry are used to search for the reaction transition state, and the reaction rate constants at different temperatures are presented. This enables students to have a more intuitive and clear understanding of transition state and reaction mechanism, and helps them learn chemical kinetics more effectively.
Journal cover is an important medium to present the research results ideologically, and further reveals the cultural backgrounds of the authors. In this paper, the covers with Chinese symbols of six well-known chemical journals from January 2011 to April 2020 have been selected. Using several typical cases, we analyze the author's considerations on the fusion with Chinese symbols in the corresponding chemical process or reaction mechanisms, and try to explore the cultural representation of Chinese symbols in the expression of chemical research results.
A novel approximate formula [H^{+}]_{p} is proposed to obtain the pH of the mixed HA and HB solutions, where[H^{+}]_{HA} and[H^{+}]_{HB} are the estimated values of[H^{+}] for HA solution and HB solution, respectively. If c_{HA} ≥ 2K_{HA}and c_{HB} ≥ 2K_{HB}, [H^{+}]_{p} formula will work very well. The novel approximation formula is simple, easy to remember, and can be widely used to calculate the pH of the mixed monoprotic weak acid HA and HB solutions.
Hydroboration of olefins is a concerted addition reaction involving only one step. It is generally considered to proceed via a four-center cyclic transition state. We performed theoretical studies on the reaction mechanism of the hydroboration of propene using quantum chemistry calculations, which led to a unique transition state that was inconsistent with the so-called four-center cyclic structure. In the computed transition state, the boron atom is bonded to both of the olefinic carbon atoms, and the degree of the hydrogen shift event is very low. All of these observations are consistent with those reported in the literature. Further theoretical studies revealed that the reaction might involve certain structures similar to the four-center cyclic structure, appearing as the transient states between the transition state and the product. Finally, the reaction mechanism of hydroboration was analyzed from the perspective of the orbital interaction model.
There are many types of organic compounds, which have caused some problems in the teaching of organic chemistry. Understanding the structures of organic compounds, and thereby obtaining clarity on the properties of organic compounds, would improve the efficiency of teaching and learning. In order to understand the structures of organic compounds, it is necessary to be familiar with carbon atom hybridization and bonding in various organic compounds. In this paper, the aforementioned hybridization is briefly summarized in the order of sp, sp^{2}, and sp^{3} hybridization.
Kinetic data treatment is one of the paramount contents of the kinetics in physical chemistry. There have been imperfections in the classical kinetic data treatment when faced with modern monitoring techniques which can supply extensive experimental data. Recently, variable time normalization analysis is raised to solve the above problems. With only several experiments under real experimental conditions, the rate constant and reaction order of the reactants and catalyst can be deduced by using visual comparison with the help of spreadsheet.
In this work, the nature and characteristics of the thermodynamic energy and thermal capacity of real gas which obeys the equation of state p(V_{m} − b)=RT are introduced. The characteristics of thermodynamic parameters in isothermal process, adiabatic reversible process, Joule experiment, and throttling process are also discussed in detail. For a real gas, fugacity coefficient and the five of thermodynamic functions of the state are presented from chemical potential equation in isothermal process.
This paper introduces a computer-aided instruction program package for teaching of acid-base titration and complexometric titration. The core parts of the package were programmed using C++ based on general expressions for acid-base titration and complexometric titration of arbitrary mixtures. The parameter file was designed to conduct operations of the software package. Users only need to write the parameter file according to a rule and then to calculate the titration curves of acid-base titration and complexometric titration of complicated system. A graphic user interface was developed to make it easy to implement the package. The package is helpful for the teaching of the theories of acid-base titration and complexometric titration.
After first established in 1835, the definition of catalyst has undergone several progresses. In 1996, IUPAC Nomenclature Committee proposed a new definition of catalyst. But till now this new definition has not been adopted extensively. In this paper, the fundamental characteristics of catalyst are listed and discussed with the essential features being clarified. Based on these discussion, a new definition of catalyst is suggested. The concept of negative catalyst is analyzed based on the essential features of catalyst. It is suggested to replace negative catalyst by inhibitor. It is meaningful for us to get a better understanding of catalyst and correct misunderstandings in the present physical chemistry textbooks.
Application of programming language R for the teaching of analytical chemistry was demonstrated with several examples. Numerical calculation of R was used to solve the high-order equations involved in chemical equilibrium. It avoided the cumbersome processes of formula simplification, and also unified all equilibrium calculations into the same method. Plotting functions of R were used to plot species distribution curves, titration curves, etc. Statistical analysis functions of R were used to replace the traditional manual method. Numerical simulation functions of R were used to help students understand complex concepts such as propagation of error and confidence interval. Compared with Excel, which is commonly used in the teaching of analytical chemistry, R also has the characteristics of being code-based, self-explanatory, flexible, rapidly evolving, and readily accessible. The application of R in teaching of analytical chemistry not only helps to improve the learning efficacy, but also provides an opportunity for students to master the powerful research tool R.
The discrepancies for calculating condensation temperature and boiling temperature for droplet and small bubble using Kelvin equation were discussed. The discrepancies can be ascribed to the neglect of variation of the vapor pressure of curved surface to plain surface with temperature, and the misusing of Kelvin equation for small bubble during boiling. The way to reduce the discrepancy is introduced while the applicability of Kelvin equation is discussed.
Structural chemistry is one of the core basic courses of chemistry-related majors. In the course of teaching structural chemistry, complex formula derivation, mathematical operations and function image drawing have always been the most difficult points of the course. This article introduces the application of the Python scientific computing library SymPy for symbolic calculation and function image drawing in the teaching of structural chemistry through specific examples. The programming language involved in the library is easy to learn, understand, and operate. It can effectively help students overcome their fear to learning, deepen their understanding of structural chemistry, and also help subsequent learning of computational chemistry courses.
The adsorption on the solid-liquid interface is important for industry and daily life. To investigate the adsorption process, the adsorption thermodynamics usually are essential. The adsorption thermodynamics are analyzed with the parameters of the change of Gibbs free energy (ΔG), enthalpy (ΔH), and entropy (ΔS). In this presentation, the different methods for calculation of the adsorption thermodynamics parameters are introduced. Moreover, examples for calculations and applications of the adsorption thermodynamics are presented.
Using web technology, the development and application of the platform of molecular point group system PGLite have been described in this paper. A friendly interface for directly accessing webpages to manipulate molecular models has been implemented, and a molecular point group display platform for structural chemistry courses has been constructed to help students better understand the molecular symmetry, which effectively improve the teaching effect of molecular point groups section.
The common points of absorption and heat transfer were found by comparison of the assumptions and transfer model. Furthermore, the computational formula and graphs of the number and the length of a transfer unit were deduced in the countercurrent heat transfer through learning from the treatment method of absorption. Based on the study, the basic analysis methodology for qualitative analysis of operational heat transfer problems was proposed. The connection between mass transfer and heat transfer was established through the comparison, so that they were no longer random knowledge points, which was beneficial for students to understand and master principles of chemical engineering.
The new names are listed for several types of common inorganic compounds such as allotropes, homopolyatomic cations, homopolyatomic anions, heteropolyatomic anions and oxyacids, based on "NOMENCLATURE OF INORGANIC CHEMISTRY – IUPAC Recommendations 2005". The characteristics of the new nomenclature have been analyzed and summarized, with emphasize on the introduction of the additive nomenclature.
Based on the quasi-classical trajectory (QCT) method and Matlab GUI technology, we developed a program code for visualizing the collision process of the elementary chemical reactions of the a + bc type. The general methodology of QCT, abstraction of dynamical properties of molecular collisions and the making of Graphical User Interface are introduced. The running results of an application to the reaction F + HCl→HF + Cl is also presented. The results showed that this program could vividly demonstrate the behavior and final state of the atom-diatom collision process in animated form. Students can interact with internal MATLAB code through graphical user interface, observe the reactive behavior and final results in real-time from multiple angles, which helps students to understand the complex reaction mechanism and deepen their perceptual impression of the chemical process at a microscopic atomic/molecular level.
In teaching electrochemistry, Materials Studio and VESTA softwares are used to assist the teaching of the structure of electrode materials and factors affecting the catalytic activity of catalysts, which makes the relevant teaching content easy to understand. This not only stimulates students' interest in the course of electrochemistry and improves the classroom teaching effect, but also helps to cultivate students' scientific thinking and exploration ability.
Taking the determination of the composition of calcium phosphate and the recovery of chromium waste liquor as the example, this paper discussed how to use Python to deal with the curve drawing and precise solution of the related problems in the design of analytical chemistry laboratory. Using Python for analysis, the process is more concise and intuitive, which can provide a better theoretical basis for experimental design.
In this paper, we discussed several problems on calculation of reaction rate constant in physical chemistry reference books. When calculating the rate constant k of the second-order reaction, we should make the half-life formula consistent with the reaction stoichiometric equation. And when calculating the activation energy with Arrhenius formula for ideal gas-phase reaction, attention should be paid to identifying the difference between the reaction rate constant k_{c} and k_{p}, as well as the difference between corresponding activation energy E_{ac} and E_{ap}. It is beneficial for students to have a correct understanding in calculation.
The concept of solid angle is used to explain the necessary and sufficient conditions for a three-dimensional gapless structure to be achieved by combining one or several polyhedrons. In this paper, the solid angle and dihedral angle of the common regular polyhedron and the common Archimedean semi regular polyhedron are presented, and the examples of structural chemistry are analyzed. In space, the sum of solid angles must be equal to 4π(sr), so by simply adding, we can judge the possibility of gapless accumulation, know the common situation of each point, and then deduce the space structure. By using this method, we can predict some structures that do not exist yet.
Using mobile internet technology, a smartphone application (app) on chemical reactivity of common heavy metal ions was designed and exercised. The app enables students to access a variety of chemical reactions between heavy metal ions and bases as well as anions commonly used in chemistry laboratory, aiming at facilitating students' ability to summarize and memorize the chemical reaction characteristics of these heavy metal ions. A random quiz is then made to enhance the understanding and using of knowledge. The app can be used for either in-class or laboratory teaching.
According to the characteristics of inorganic chemistry and in view of the current problems in classroom teaching of inorganic chemistry, the computational chemistry assisted teaching model has been introduced in this paper. The implementation of this innovative model is not only helpful for students to understand the difficult knowledge of inorganic chemistry, but also popularize the practical application of computational chemistry, which provides an opportunity for the establishment of the big data platform of chemistry in colleges and universities.
The quantitative calculation of pH of monoacid/monobasic solution is a basic problem for inorganic chemistry teaching. The qualitative description and quantitative calculation of pH are connected by approximation conditions. It is very important for the students to understand these approximation conditions, which will help them solve problems about ionic equilibrium in aqueous solution. However, how to use these approximation conditions correctly in solution of low concentration and weak acids is often difficult. Even in some textbooks, the description of concepts is not accurate and not consistent with the associated courses. Thus, to solve the problems mentioned above, the derivations of the approximation conditions are introduced and examples are analyzed in detail in this paper. The problems of quantitative calculation of pH of monoacid/monobasic solution which should be paid attention to in the course teaching of inorganic chemistry are discussed.
This paper provides a practical explanation of the comparison between nucleophilicity and basicity of nucleophiles. The similarities are explained based on the principle of "structure determines property", and the differences are explained by combining Hard-Soft-Acid-Base theory and the steric hindrance factor.
In the substitution and elimination reactions of haloalkanes, the attacking reagents are all negatively charged entities or multi-electron groups, so the competition reaction between substitution and elimination of haloalkanes is the key and difficult part of the teaching content. This article introduces the organization and design of this part of teaching contents, so that students can better understand and grasp this part including the influence of reaction substrates, attacking reagents and reaction conditions on dominant reactions and products. The instructional design plays an important role in training students' ability of analysis, thinking and flexible application of knowledge.
A statistical software package is developed for the course of chemical analysis. The software calculates cumulative distribution functions and inverse cumulative distribution functions of normal, t, χ^{2}, and F distributions; it also provides critical values for tests of statistical significance. The software is designed to substitute for traditional data tables that are insufficient and obscure. Statistical problems can be solved more efficiently with the software than with traditional data tables, which enables students to focus on understanding statistical principles and interpreting results. The software provides information through an intuitive interface, a graph, and natural interactions. Both Matlab and Android versions are presented, and free of charge.
In this paper, a simple thermodynamic model of crystal macroscopic morphology and the cause of the defects were suggested. By virtue of growing alum(K) crystals and measuring their macroscopic parameters in the inorganic laboratory for undergraduates, we can calculate the thermodynamic parameters of alum, thus explaining the macroscopic morphology and defect of alum(K), and predicting the possibility for alum(K) to generate octahedral crystals and its self-normality.
Using three-dimensional (3D) graphing and molecular modeling softwares, the procedures for presenting the VRML 3D wave functions have been discussed. The interactivities of VRML can help students to observe the characters of wave functions intuitively, which also improve the teaching results of quantum chemistry and electronic structures effectively.