Balancing redox equations through zero oxidation number method

Many high school students and first-year undergraduate students find it difficult to balance redox reactions. A method using zero oxidation number to balance redox equations is presented herein. This method may shorten the balancing time and lessen the effort. It is a helpful complement to the traditional oxidation number method and half-reaction method.

Exploring the relationships among stoichiometric coefficients, number of transferred electrons, mean oxidation number of carbons, and oxidative ratio in organic combustion reactions

Combustion reactions, stoichiometry, and redox reactions are some of the basic contents in chemistry curriculum. Although the counting of transferred electrons is critical in redox reactions, assigning mean oxidation number of organic carbons (ONc) is not always easy. Even though the relationship between the oxidative ratio (OR) and ONc is known, the relationship between the number of transferred electrons (Te−) and OR has not been thoroughly studied. The H-atom method has already been developed to balance and deduct organic combustion reactions. It can be used further to help establish the relationships among the stoichiometric coefficients (SC), the number of transferred hydrogens (TH), and Te−. This article uses the procedures of the H-atom method for balancing and deducting, and the known relationships among SC, TH, and Te− for exploring the relationships among SC, Te−, ONc, and OR in organic combustion reactions. By integrating three sets of relationships: (i) SC and Te−, (ii) Te− and ON, and (iii) SC and OR, the interconversions among SC, Te−, ONc, and OR can be mathematically formulated. Furthermore, Te−, ONc, and OR can be assigned by SC and the general molecular formula of CxHyOzXw.

A simple theoretical, quantitative approach to help understand the titration of weak acids and bases

What happens at the very beginning of the titration of a weak acid or base is a question sometimes asked by undergraduate students when introduced to the concept of buffer solution. To attempt to answer this question, a simple quantitative approach is developed, which also allows explaining more general properties of the weak acid or weak base titration process, while serving as well as an introduction to the theoretical, quantitative treatment of this subject. Using this approach, it can be shown that, at the beginning of the titration, the reaction between a weak acid (base) and a strong base (acid) does not occur on a one to one ratio when very small amounts of the strong base (acid) are added.

A new spin on electrochemistry in the undergraduate lab

The growing interest in electrochemistry over recent years has sparked an increase in the popularity of various electrochemical techniques, including more advanced methods, that have previously been overlooked in academia and industry. This makes comprehensive hands-on experience in electrochemistry a highly demanded addition to chemistry graduates. However, many students do not receive sufficient training in the theory and experimental design to confidently use and apply various electrochemical techniques throughout their undergraduate, and sometimes even in graduate studies. Here we summarize the theory and practical applications for both rotating disk electrode (RDE) and rotating ring disk electrode (RRDE) techniques. The different modes of operation of rotating ring disk voltammetry, methodologies of data analysis and interpretation as well as the scope of the information that can be extracted from the RDE/RRDE are discussed. Proposed modifications of the laboratory curriculum will allow students to examine and learn valuable information about the reactions on the surface of the electrode/liquid interface. This information will allow chemists to confidently use RDE and RRDE techniques for a wide range of research and development targets. Furthermore, incorporating these techniques into existing chemistry laboratories will help chemistry educators to enrich the undergraduate chemistry curriculum and improve students’ learning outcomes.

Learning Green Chemistry and its principles from Nature’s process and development of green procedures mimicking nature

We have highlighted an example of a natural process like photosynthesis to introduce the subject of Green Chemistry. Photosynthesis can be an ideal example to illustrate a green process explaining all the features such as selection of raw materials, solvent, catalyst, energy, etc. for an environment-friendly reaction. From the same reaction, all the principles of Green Chemistry can be derived in a simpler way without the need of memorizing these in a set language. In this article, a few examples of green procedures for the synthesis of useful molecules have been illustrated in light of the knowledge of photosynthesis. The visible-light mediated reactions, organic reactions in water, and solvent-free organic reactions are discussed here for a practical illustration of Green synthesis.

Understanding Le Châtelier’s principle fundamentals: five key questions

The well-known Le Châtelier’s principle is almost always mentioned when dealing with chemical equilibrium. Nevertheless, although a must in most general chemistry courses starting from the secondary level, when students face questions about it, some major misconceptions are often highlighted; to avoid this, a somewhat challenging problem is now presented. It can be deemed a very useful tool for a full understanding of this principle and chemical equilibrium as a whole. A generic chemical reaction at equilibrium is subject to different types of perturbation, and the student is required – in each case – to identify the new position of equilibrium among a number of proposals. The correct answers are finally provided along with the corresponding explanations.

New approach for assigning mean oxidation number of carbons to organonitrogen and organosulfur compounds

Organonitrogen and organosulfur compounds are abundant in the natural environment. To understand the biological redox pathways properly, it is important for learners to be able to count the oxidation number of organic carbons. However, the process of counting is not always easy. In addition, organonitrogen and organosulfur molecules are seldom studied. To compensate these problems, this paper explores the bond-dividing method, which can effectively determine the mean oxidation number of carbons of organonitrogen and organosulfur molecules. This method uses the cleavage of carbon-sulfur and carbon-nitrogen bonds to obtain the organic and inorganic fragments. The mean oxidation numbers of carbon atoms, nitrogen atoms, and sulfur atoms can be calculated by the molecular formulas of their fragments. Furthermore, when comparing organosulfur or organonitrogen molecules in a redox conversion, the changes of the mean oxidation numbers of carbon atoms, nitrogen atoms, and sulfur atoms can be used as indicators to identify the redox positions and determine the number of transferred electrons.

Illustrating catalysis with a handmade molecular model set: catalytic oxidation of carbon monoxide over a platinum surface

Catalytic converters (automotive catalysts) and the chemical reactions they catalyze appear in general and introductory chemistry textbooks. Although the detailed mechanisms of the chemical reactions that occur in catalytic converters have been clearly revealed via recent developments in surface and computational chemistry research, the description and illustration of the catalysis are still ambiguous in textbooks. In this paper, we describe an extracurricular lecture whereby a handmade teaching aid was employed to illustrate the basic principle of the catalytic oxidation of carbon monoxide over platinum surface, which is an essential reaction occurring in catalytic converters. The teaching aid, constructed combining easily available materials, can illustrate the positions and motions of the molecules on the platinum surface during catalytic oxidation. The lecture was favorably received by non-chemistry majors and high school students. Despite the difficulty of the topic, the audience displayed a relatively high level of understanding.