Acids and bases are chemical compounds always present in our daily life. They are important raw materials in manufacturing industries and are necessary for the control of various industrial processes. They participate actively in living organisms’ metabolism and, if improperly disposable they can alter the environmental conditions necessary to the human well-being. Acids have sour taste (e.g. citrus fruits), while bases have astringent flavors (“soap like”). In addition, theses substances are part of cosmetic formulations, food, drinks, pharmaceuticals, cleaning products, toiletries, etc.. The most common way to determine the acidity or alkalinity of an aqueous solution is measuring its pH, but this concept is not as simple as it seems to be.

Keywords
acids, bases, acid-base theories, pH, the concept of pH, pH scale, acidity, alkalinity.

Authors
João Carlos de Andrade
Universidade Estadual de Campinas, Instituto de Química

The Chemical and physical phenomena and the principles applied in qualitative analysis to identify ions in aqueous solution are the same ones used in quantitative analysis of different samples and are still used in many official reference methods, including instrumental methods or procedures. This shows the importance of knowledge of the fundamentals of qualitative analysis, requiring the teacher to get the students’ attention for their practical applications. Below are some brief descriptions of methods and procedures as suggestions for class discussion.

Keywords
qualitative analytical chemistry, quantitative analytical chemistry, concepts, applications, experiments, learning, testing methods, ASTM, AOAC, RSC.

Authors
João Carlos de Andrade
Universidade Estadual de Campinas, Instituto de Química
Terezinha Ribeiro Alvim
Centro Federal de Educação Tecnológica de Minas Gerais, Departamento de Química – CEFET-MG

Obeying the fundamental law of nature that says, “a physical or chemical system always tends to cause an irreversible change from some state of initial non-equilibrium to a final equilibrium”, chemical reactions can be defined as processes in which different substances interact with each other, with a rearrangement of atoms occurring that completely changes the initial characteristics of the substances involved, tending to an equilibrium. This article shows, in a concise manner, the kinetic and thermodynamic aspects of equilibrium in aqueous solution.

Keywords
equilibrium, electrolytes, activity, activity coefficient, ionic strength, Debye-Hückel, kinetics, thermodynamics.

Author
João Carlos de Andrade
Universidade Estadual de Campinas, Instituto de Química

The content of Inorganic Qualitative Analytical Chemistry usually used by Brazilian Higher Education Institutions (HEIs) covers the theory of chemical equilibrium in aqueous solution and, in the laboratory, the separation and identification of cations and anions in solution or solid samples, using classical methods. As there are still opinions both fory and against the maintenance of classic Qualitative Analytical Chemistry in the curriculum of Brazilian higher education in chemistry, this section intends to provide evidence demonstrating of the importance of teaching about research of cations and anions in the formation of chemists in Brazil, as a fundamental basis for the teaching of Quantitative Analysis and Instrumental Analysis.

Keywords
Qualitative Analytical Chemistry, data collection, formation of chemists, cation separation reactions, cation identification reactions, anion identification reactions, analytical steps, reaction medium, operational care, Pedagogy.

Authos
João Carlos de Andrade
Universidade Estadual de Campinas, Instituto de Química
Terezinha Ribeiro Alvim
Centro Federal de Educação Tecnológica de Minas Gerais, Departamento de Química – CEFET-MG

History shows that nothing is totally new and therefore the old should not be discarded, but known so that new knowledge can be constructed. Thus, when interviewed by Rudy M. Baum, Henry Taube, Nobel Prize in Chemistry in 1983, said that the disappearance of qualitative analysis from the curriculum of American universities was a mistake, because that was a way to introduce descriptive chemistry and motivate students to study chemical reactions that, in his opinion, “are the heart of chemistry” [1]. In view of this controversy and of the possible options for the use of the discipline of Qualitative Analytical Chemistry as a tool for the education of chemical equilibrium in aqueous solution, a critical view of the historical sequence of the procedures for qualitative analysis development is presented below.

Keywords
classical analysis, Qualitative Analytical Chemistry, education, history, applications.

Authors
João Carlos de Andrade
Universidade Estadual de Campinas, Instituto de Química
Terezinha Ribeiro Alvim
Centro Federal de Educação Tecnológica de Minas Gerais, Departamento de Química – CEFET-MG

Some analytical techniques, such as voltammetry, are relatively little used in undergraduate experimental disciplines in chemistry (and related sciences), although addressed in theoretical ones. Since, in contrast to what one thinks, voltammetric measurements are still often used in routine analysis, some of the most direct techniques will be highlighted in this text, with suggestions to the reader who seeks more knowledge on this theme. The experiments presently proposed present a well defined conceptual and methodological character and have been tested in the experimental classes of the Instrumental Analytical Chemistry discipline of the Institute of Chemistry at UNICAMP. Each module is proposed for four hours of activities in the laboratory, with low risk.

Keywords
voltammetry, water, sugarcane liquor, fruit juices, nickel, cobalt, copper, cadmium, zinc, ascorbic acid

Authors
João Carlos de Andrade
Audrey de Arruda Falcão
Elaine Castilho Guedes
Universidade Estadual de Campinas, Instituto de Química

Translated by
João C. de Andrade

Revised by
Carol H. Collins

Warning

Attention: “Read carefully the procedure before starting the experiment. Do not perform the experiment without being monitored by your teacher. In doubt ask for help!”

Until 1960, catalysts based on coordination compounds were little used and they were mainly employed on the laboratory scale. Since then, however, there has been a rapid emergence of new catalytic systems, mainly due to developments in Organometalic Chemistry, due in large part to the use of organometallic complexes (and / or coordination compounds) in three industrially important reactions: the Ziegler, Wacker and Oxo processes. Appropriate combinations of ligands (electronic and stereo effects) strongly influence the structure and the reactivity of catalytically active complexes. With the increasing knowledge of the coordination chemistry, in particular Organometalic Chemistry, it is possible to get the exact structure of the complex which will catalyze a reaction. Nowadays, the use of “clean” chemical reactions is a requirement, not only in the chemical industry, but also in the laboratory. By using highly efficient and selective catalysts it is possible to save energy and raw material, which is the case of complexes of transition metals. In order to understand catalysis by transition metals it is necessary to know the chemistry of the complexes involved: organic reagents are primarily coordinated to the metal as ligands (i.e., are activated) and are then converted to products through various types of reactions. It is therefore necessary to review some fundamental aspects such as structure, binding and reactions of metal complexes to better understand the phenomena involved in catalysis.

Keywords
catalysis, catalysts, catalytic systems, coordination compounds, organometallic compounds, ligands, coordination sphere, chemical structure, chemical bonds, metal complexes

Author
Regina Buffon
Universidade Estadual de Campinas, Instituto de Química

Translated by
João C. de Andrade

Revised by
Carol H. Collins

Initially the ideas of classical magnitude and classical body, continuous media, temporal and constitutive functions, density and rate will be shown, the latter being related to the rudimentary concepts of derivatives and functions. Then the concept of property is indicated, without the use of mathematical expressions, as well as the classification of properties into intensive, extensive and additive extensive. In addition, the concepts of exact and inexact differential equations are discussed and related to that of property. In this discussion, it is shown the illogic and inherent inopportunity use of more than a single mathematical symbol to represent the differential of a variable, from an erroneous concept of differential. The exact concept is then briefly described.

Keywords
thermodynamic properties, functions of state and process, exact and inexact differential equations, line integrals, extensive and intensive properties, thermodynamic state, temporal and constitutive functions, thermodynamics of homogeneous media, thermodynamics of continuous media

Author
Adalberto B. M. S. Bassi
Universidade Estadual de Campinas, Instituto de Química

Translated by
João C. de Andrade

Revised by
Carol H. Collins

Besides conceptual and quantitative aspects, studies in chemistry should involve experiments with a demanding high level of care and attention in the use of experimental techniques. Considering these aspects, the determination of the molar mass of a metal, through the volume of gas released by its reaction with an acid, is an ideal experiment to achieve these purposes. This work addresses important concepts such as the “molar mass” and the “standard electrode potential”, through accurate results obtained by using simple experimental techniques such as weighing, measuring volumes and the preparation of solutions. The first didactic experiment used to discuss and contextualize these concepts in a single experiment was published in 1937 in the Journal of Chemical Education, although the reaction of magnesium with different acids had already been discussed (in terms of the Bronsted-Lowry’s acids theory) in 1931, in this same journal. Some highlighted words in the text are listed in the Glossary of Terms, Definitions and biographies, annexed to the main text.

Keywords
reaction of metal with acid, stoichiometry, law of ideal gases, determination of molar mass, standard electrode potential, weighing, volume measurement, preparation of solutions

Authors
Janaína César
João Carlos de Andrade
Universidade Estadual de Campinas, Instituto de Química

Translated by
João C. de Andrade

Revised by
Carol H. Collins

Warning

Attention: “Read carefully the procedure before starting the experiment. Do not perform the experiment without being monitored by your teacher. In doubt ask for help!”

The method of response surface analysis is employed to optimize the catalytic response of the Mo (VI) in the oxidation reaction of iodide ions by hydrogen peroxide, using the fixed time method. The absorbances of the non-catalytic reaction and the catalytic action of Mo (VI), the delta, were modeled. This was done in detail to illustrate the importance of careful result evaluation, which is not always emphasized due to the necessary mathematical rigor and the difficulty of users of multivariate techniques in dealing with this language. The example presented in this text shows that only the analysis of variance (ANOVA) is not a sufficient criterion for the selection of a model that can describe a particular set of data, being essential the analysis of the graph of residuals, keeping a critical view of the results. The twenty-four trials of the factorial design originally employed in the modeling (twelve in the absence and twelve in the presence of molybdenum), and subsequently extended to a star design (eight trials), can be performed in a experimental discipline within 4 to 6 hours, allowing its inclusion in an experimental course at the undergraduate level to introduce the use of multivariate optimization. The use of a procedure for extraction of iodine generated in situ can also “freeze” the catalytic reaction in a pre-determined reaction time, allowing the realization of a large number of experiments efficiently by means a batch process, making it possible to obtain the necessary data for the construction of mathematical models.

Keywords
response surfaces, analysis of variance, ANOVA, multivariate optimization, graph of residuals, experimental design, modeling

Authors
Aline Renée Coscione
Audrey de Arruda Falcão
João Carlos de Andrade
Universidade Estadual de Campinas, Instituto de Química

Translated by
João C. de Andrade

Revised by
Carol H. Collins