The chemical and physical properties of tetravalent lanthanides: Pr, Nd, Tb, and Dy

The thermochemistry, descriptive chemistry, spectroscopy, and physical properties of the tetravalent lanthanides (Pr, Nd, Tb and Dy) in extended phases, gas phase, solution, and as isolable molecular complexes are presented.

Progress of Digital Learning Resources: Development and Pedagogical Integration of a Virtual Environment Laboratory for the Practical Experiments in Chemistry

The work presented in this paper aims at applying a new complementary computer methodology to the teaching of chemical science including the use of a virtual environment laboratory that has an alternative value for the simulation of practical experiments in chemistry. This study is based on two axes, the first deals with the implementation of a laboratory for simulation that helps to carry out various practical work of chemistry. The second axis aims to demonstrate the pedagogical impact of the use of virtual learning environments on the teaching-learning process in the university curriculum. To study the necessity and the feasibility of this technological tool we took as a case study the exploitation of the periodic table in the descriptive chemistry and the practical works of chemical kinetics. In this article we used a strategic methodology to meet the validation constraints of our computer tool thenwe conducted a qualitative study on a sample of students from the Physical Chemistry of Materials Laboratory at the Ben M'sik Faculty of Science to identify the didactical factors influencing the progress of the practical work using our computer solution.

The Construction of E–pH Diagrams

In order to construct an E–pH diagram one needs to follow eight basic steps: (1) Select the species of the element involved which contain one or more of the following entities: the element, oxygen, and hydrogen. This is best done by reading the descriptive chemistry of the element in a good inorganic text and identifying the species, both soluble and insoluble, which persist, at least for several minutes, in aqueous solution. (2) Starting at the lower left-hand corner of an E–pH framework, arrange the selected species in vertical order of increasing oxidation number of the element. Then, if there are different species with the same oxidation number, arrange them in horizontal order of decreasing protonation (increasing hydroxylation). If there is only one species of a given oxidation number, this species extends across the entire pH range for the purposes of diagram construction. (3) Draw in border lines between the species, that is, the lines representing the transformation of a species to another species. You will not know exactly where these lines occur but the approximate regions are sufficient for the purposes of diagram construction. (4) Write equations for the transformations that have been indicated. Some of them will involve electrons and therefore will be half-reactions. Such equations must always be written as reductions, that is, with the electrons on the left. In addition, no reaction should contain the OH− ion; only the H+ and/or HOH instead. (5) From appropriate tabulations, obtain the standard free energy values (ΔG° in kJ/mole) of every species in the equations. These ΔG° values are to be employed in the following relationship which applies to each of the above equations. . . . ΔG° (reaction) = ∑ΔG° (products) − ∑ΔG° (reactants) (6) . . . (6) The ΔG° (reaction) values for each equation are to be converted into E° values for those equations containing electrons and into K values for those equations which do not. This is done by use of the following expressions: . . . E° = ΔG° /−96.49n log K = ΔG° /−5.7 (7/8) . . . where n represents the number of electrons in an equation.