Volume 4, Issue 3

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.

Defining and balancing redox reaction requires both chemical knowledge and mathematical skills. The prevalent approach is to use the concept of oxidation number to determine the number of transferred electrons. However, the task of calculating oxidation numbers is often challenging. In this article, the H-atom method and O-atom method are developed for balancing redox equations. These two methods are based on the definition of redox reaction, which is the gain and loss of hydrogen or oxygen atoms. They complement current practices and provide an alternate path to balance redox equations. The advantage of these methods is that calculation of oxidation number is not required. Atoms are balanced instead. By following standard operating procedures, H-atom, O-atom, and H 2 O molecule act as artificial devices to balance both inorganic and organic equations in molecular forms. By using the H-atom and O-atom methods, the number of transferred electrons can be determined by the number of transferred H-atoms or O-atoms, which are demonstrated as electron-counting concepts for balancing redox reactions. In addition, the relationships among the number of transferred H-atom, the number of transferred O-atom, the number of transferred electrons, and the change of oxidation numbers are established.

We investigate how chemistry-teacher students and teachers interpret chemical equations regarding the sub-microscopic level of solid ionic salts and their solutions. Addressing participants’ skills in making sense of chemical formulas might significantly influence students’ conceptual understanding: ionic salts formulas like Na 2 CO 3 (s), CaCO 3 (s), MgO(s) were established in the questionnaire. A coding system used to reveal participants’ reasoning correspond to their misconceptions. The enrolled participants were 101 undergraduate chemistry education students from Indonesia and Ethiopia and 24 chemistry teachers from Indonesia and Tanzania. Our results showed students’ and teachers’ difficulties in figuring out the involved ions of provided salts and interpreting the chemical formulas. Consequently, general chemistry learning should provide better fundamental knowledge on the submicroscopic level based on involved particles like atoms, ions, and molecules. It would also be helpful to introduce an appropriate sequence of historical ideas to find the existence of atoms, ions, and molecules.

Gender issues, and specifically the lack of women in the physical sciences, has been a subject of intense debate for decades. The problem is so acute, that national initiatives have been developed to analyse and address the issues, with some success in STEM, particularly in higher education and also in industry. However, despite this progress, there is little understanding as to why women are less likely to study the chemical sciences in particular. In this research, a survey and interviews were used to find out why female A-level chemistry students choose, or do not choose, to study chemistry at higher education level. Two distinct phases were identified. Firstly, intelligence gathering to understand the location, content, entry requirements, and career options for potential course and institution combinations. Secondly, self-reflection to establish whether, knowing themselves, students feel as though they would be successful on a particular course at a particular institution. These findings align with research into gender imbalance in STEM and Higher Education more broadly, but go beyond this to broaden current debates with a focus on chemistry in particular.

Teaching practical laboratory skills is a key component of preparing undergraduate students for future careers in chemistry and elsewhere. In this paper, we present our new strategy to teach practical skills to undergraduate chemistry students. We report a Skills Inventory, a list of the suggested practical skills a graduate chemist should possess; this list was compiled by chemists across the UK. In our new practical course we begin by decoupling the practical skill from the theoretical background, compelling students to first master the basic processes needed to carry out a specific technique. In what we have termed a ‘spiral curriculum’ approach, skills are revisited on multiple occasions, with increasing complexity and greater emphasis on underlying theory. The new course makes links across traditional subdisciplines of chemistry to avoid compartmentalisation of ideas.

In this paper, we describe and evaluate a study on the use of mechanism comics for writing solutions to a task in a written exam for the course “Organic Chemistry I for Pre-Service Chemistry Teachers.” The students had to design a reaction mechanism for a reaction that was unknown to them and write captions explaining every step of their reaction mechanism. The students’ work was evaluated using the method of qualitative content analysis in four rounds by both authors. The majority of the captions were coded as “descriptive” and only a minority as “causal.” This means that the students mostly described “what” happened, but seldom “why” this happened. Implicit electron movement was also described more often than explicit electron movement. The majority of the captions were technically correct. In summary, the students were capable of designing and describing a reaction mechanism for a previously unknown reaction. The quality of their reasoning could be improved, however. In the new course, the quality of students’ mechanistic reasoning and then especially their explanations of “why” mechanistic steps occur will be given much clearer emphasis.

We describe simple, quantitative, graphical approach to solve chemical equilibrium problems and quantify how far the reversible reaction advances upon reaching equilibrium state at a given temperature. The same approach also gives the change in reaction advancement ratio (reaction efficiency; % completion of reaction) upon perturbation of equilibrium state by changing equilibrium concentrations (moles) of reactants or products. The approach is based on plotting two polynomial functions which represent how the numbers of moles of reactants and products vary with the advancement of reaction. The point of intersection of the two polynomial curves (functions) gives advancement ratio for a reversible reaction at equilibrium ( χ e ). In comparison, Le Chatelier’s principle is qualitative and tells us that equilibrium concentrations (moles) of products will increase (or decrease) once concentrations of reactants are made larger (or smaller), but does not predict the change in advancement of reversible reaction upon re-establishing the equilibrium state. In other words, it does not specify whether after perturbation the conversion to products will result in higher or lower reaction efficiency. Our quantitative approach is complementary to the qualitative Le Chatelier’s principle and is applicable to any single-equation equilibrium system. It can also be an alternative to ICE tables.

The identification of undergraduate chemistry students’ conceptual difficulties and common mistakes with basic concepts and problems in chemical kinetics provided the aim for this study, which involved 2nd-year/4th semester students who had passed the chemical kinetics component of a physical chemistry course. The study involved the analysis, evaluation and interpretation of students’ answers to the final examination in chemical kinetics. Three achievement groups, for the various topics, were identified: Group A, high achievement (mean ≈ 85%): (a) the steps in a chain-reaction mechanism, (b) integrated 1st- and 2nd-order rate laws; and (c) the Lindemann–Hinshelwood mechanism. Group B, intermediate achievement (mean ≈ 74%): (a) half-life, (b) instantaneous rate and the extent of reaction variable ( ξ ), (c) the Michaelis–Menten mechanism, and (d) theoretical rate law not asking for a final formula. Group C, low achievement (mean ≈ 54%): (a) experimental rate law and the reaction rate constant on the basis of an experimental-data table, (b) extracting the theoretical rate law, and (c) the Arrhenius equation. Students’ errors and misconceptions have also been identified. Successful students tended to respond well to straightforward questions on the theory of the subject, but had difficulties when solving problems. It is essential that teachers understand the potential of their students, especially possible misconceptions they may hold, and the teaching approaches that may contribute to overcoming the student difficulties. Problems in chemical kinetics can be very demanding both in terms of algebraic manipulations and conceptually. Teaching should focus on problem solving, with the emphasis on students themselves trying to solve the problems.