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!”

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

Many students think that density is simply the result of an arithmetic operation of division between mass and volume of a substance, but this concept is much broader and is related to others, such as compression and packing. For example, the greater the packing of atoms the more dense is the substance. Similarly, the greater the compression on an object, the greater will be its density. In this work only the most direct and most common laboratory techniques involved in the determination of the densities of solids and liquids will be discussed, but it is worth a more profound description of the concept of density. The proposed experiment, conceptual and methodological in character, has duration of two hours of activities in the laboratory, with a low level of risk.

Keywords
density, absolute density, relative density, chemical properties, physical properties

Authors
Janaína Cesar
Marco-Aurélio De Paoli
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!”

In this text the basic safety procedures to be followed in a chemistry laboratory are indicated. They should be Incorporate into your daily work procedures.

Keywords
safety, laboratory chemicals, hazardous reactions, waste

Authors
Aline Renée Coscione
Alex Magalhães de Almeida
João Carlos de Andrade
Rogério Custodio
Universidade Estadual de Campinas, Instituto de Química

Translated by
João C. de Andrade

Revised by
Carol H. Collins

The safety regulations of the Institute of Chemistry at Campinas State University determine the basic requirements for the protection of life and of locations where chemicals and equipments are used. These regulations apply to all persons located in the Institute of Chemistry and also to those who are not connected to it, but have authorized access to its facilities.

Keywords
laboratory chemicals, chemical reagents safety, waste, regulations

Translated by
João C. de Andrade

Revised by
Carol C. Collins

The equipment known as the breath alcohol analyzer allows the determination of the amount of alcohol in the blood, ingested in the form of ethanol in alcoholic beverages, through the breath of a person. This determination is based on the principle that the alcohol contained in the blood is in equilibrium with the alcohol in the air in the lungs. The proposed experiment describes a procedure for determining the amount of alcohol present in a sample of alcohol vapor, simulating the conditions of a breath alcohol analyzer. The main objectives are:

• Discuss, in general, the principles used in a chemical breath alcohol analyzer.
• Introduce spectrophotometric methods of analysis and illustrate thier application.
• Introduce the use of the linear regression method to fit experimental data and demonstrate its use in obtaining the equation of an analytical calibration curve.
• Determine the amount of ethanol in the vapor of a alcohol sample, simulating the conditions  of a breath alcohol analyzer used for determining the alcohol vapor based on the oxidation of alcohol by dichromate ions.

Keywords
breath alcohol analyzer, alcohol, ethanol, spectrophotometer, determination of ethanol, chemical analysis, linear regression, calibration curve

Autores
João Carlos de Andrade
Aline Renée Coscione
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!”

This text is intended to outline the basic procedures for the handling of substances in glass ampoules to be closed and / or opened in the glass workshop, and to establish the need for their compliance.

Keywords
glass ampoules, rules, chemistry laboratory, glassware, handling procedure

All necessary precautions for the use of the Laboratory for Dangerous Reactions at the Institute of Chemistry (UNICAMP), as well as directions to be followed and the terms of liability which must be previously delivered to the Safety Committee are presented here.

Keywords
laboratory chemicals, chemical reagents, safety, waste, regulations

Translated by
João C. de Andrade

Revised by
Carol C. Collins

Volumetric methods using oxidation and reduction reactions depend on the potential of half-reactions involved but, beyond favorable potential conditions, the oxidizing and reducing agents must be stable in solution and the substance to be determined should have a stable oxidation state, defined before the titration is started. Iodometry is an indirect volumetric method, where an excess of iodide ions are added to a solution containing the oxidizing agent, which react producing an equivalent quantity of iodine that is then titrated with a standardized solution of sodium thiosulfate.

Keywords
half-reactions, oxidation state, volumetry, redox reactions, oxidizing agents, reducing agents, iodometry

Author
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!”