Didactic Experiments Using Voltammetric Measurements

Author: João Carlos de Andrade; Audrey de Arruda Falcão; Elaine Castilho Guedes
April 2007

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 Concept of Thermodynamic Properties

Author: Adalberto B. M. S. Bassi
May 2006

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, [...]

The Two Expressions of Fundamental Thermodynamics

Author: Adalberto B. M. S. Bassi
April 2006

Here, some of the most typical concepts of thermodynamics, namely heat, internal energy, entropy and temperature are used for complementary understanding of the concepts of the enthalpy and energy of Helmholtz and Gibbs. The entropy concept has already been presented by this author, along with some of the concepts of temperature and the energies of [...]

Entropy and Helmholtz’s and Gibbs’ Energies

Author: Adalberto B. M. S. Bassi
November 2005

Traditionally, the concept of entropy exists only for equilibria, which then require the same for the Helmholtz’s and Gibbs’ energies, because these are defined from it. As a result, all thermodynamics is restricted to equilibria, although it usually includes quantities classified as mechanical, such as volume and internal energy, which are considered outside the existing [...]

Mathematics and Thermodynamics

Author: Adalberto B. M. S. Bassi
September 2005

Mathematics and Thermodynamics seem to be immiscible. Thermodynamicists take their own mathematical path which needs to return more than a century in time to meet the actual science done presently by mathematicians. Mathematicians are usually not interested in thermodynamics, and when they are, their work is not easily understood by thermodynamicists. Although both seem very [...]

The Base Functions: The Variational Adjustment

Author: Nelson Henrique Morgon; Rogério Custódio
February 2001

Among the mathematical models used to represent the electronic structure of microscopic systems one of the most valuable is the Hartree-Fock model. The major problem to be solved in this model is the choice of the mathematical functions to be used to represent the Hartree-Fock orbitals. One of the most important suggestions for the Hartree-Fock [...]

Qualitative Aspects of the Orbital Model

Author: Noemí Marta Torres
May 2000

The mathematical complexity involved in the quantum theory is beyond the level of general chemistry courses and has led to the use of excessive simplifications. Although this situation is being discussed in the literature over the past 20 years, an inconsistent approach to the principles of quantum theory and experimental observations, even though emphasizing the [...]

Quantum Mechanics Postulates

Author: Rogério Custodio; André Severo Gomes; Lucimara Ramos Martins; João Carlos de Andrade
March 2000

Understanding of the nature of the atoms, molecules and more complex system properties is directly related to the distribution and behavior of their microscopic particles. Somel experimental evidence suggests that the structure of atoms and molecules could not be explained by principles based on classical mechanics. Experiments, such as black body radiation, heat capacity and [...]

The LCAO Method

Author: Rogério Custodio; Nelson Henrique Morgon; João Carlos de Andrade

Atomic and molecular orbitals can be obtained as a linear combination of basic functions. This model is known as the method of linear combination of atomic orbitals (LCAO), one of the techniques most used for calculating the electronic properties of atoms, molecules, etc., by quantum methods. This text will address some of the key points [...]