New Approaches
Chemical Reactions Do Not Always Moderate Changes in Concentration of an Active Component
Резюме. It is shown in this paper that the use of Le Chatelier’s principle as a Principle of Moderation fails. It is discussed moderation of mole fractions and moderation of molar concentration (molarity) in a reaction of ideal gases. An analysis carried out on thermodynamic grounds allows us to conclude that this system moderates the increment of molar concentration (molarity) of an active component, but this same system does not moderate the increment of mole fraction of an active component at constant T and V.
Keywords: chemical equilibrium, changes in concentration, Le Chatelier’s principle, moderation of molar concentration, moderation of mole fractions
J.J. Solaz-Petroles, V. Sanjose
Влезте в системата, за да прочетете пълната статияLetters to the Editor
Dimensional Analysis: An Example [In Bulgarian]
V. Tonchev
Влезте в системата, за да прочетете пълната статияNew Approaches
Recasting the Derivation of the Clapeyron Equation into a Conceptually Simpler Form
Резюме. The Clapeyron equation specifies the variation of the pressure, P, with respect to the temperature, T, of a closed two-phase one component system at the phase boundary under conditions of thermodynamic equilibrium. Even though in the context of the traditional derivation of this equation (as presented in most books on undergraduate/postgraduate Physical Chemistry or Thermodynamics), Gm,i (P, T) (where i = 1 and 2) curves are not presented, the derivation involves the consideration of two points on each of these curves subject to the condition that the two phases are in equilibrium with each other. Geometrically, this implies the separate movement from an initial to a final point (in the neighborhood of the initial point) on the two Gm,i (P, T) (where i = 1 and 2) curves which incidentally are congruent at the phase boundary. At first glance, however, it is not trivial to geometrically (graphically) visualize this movement from the equations that are presented in the traditional derivation of the Clapeyron equation, thereby, possibly causing a certain amount of confusion. In the present work, a conceptually simpler and mathematically rigorous derivation of the Clapeyron Equation is presented where the quantity of interest that is considered is ∆Gm(P,T) = Gm,1(P,T) – Gm,2(P,T). ∆Gm(P,T) is equal to zero at the phase boundary and, thereby, d∆Gm(P,T) is also equal to zero at the phase boundary. This key idea then makes it possible to focus on a single point in the ∆Gm(P,T) curve that occurs at the phase boundary between the two phases in deriving the Clapeyron Equation and also to geometrically visualize the phase equilibrium situation.
Keywords: Clapeyron equation, phase equilibria, chemical thermodynamics, molar Gibbs energy, equilibrium thermodynamics
S. Murthy
Влезте в системата, за да прочетете пълната статияCurriculum Matters
Critical Remarks on the Matriculation Exam in Geography in 2013 [In Bulgarian]
Резюме. The results and quality of questions for school-leaving examination in “Geography and Еconomics†in Bulgarian secondary school in 2013 are commented. The paper reveals some of the weaknesses of the existing practice of designing of the state tests in geography for graduating from the secondary schools.
Keywords: school-leaving examination, matriculation, geography, quiz-making analysis
I. Drenovski
Влезте в системата, за да прочетете пълната статияCurriculum Matters
Contemporary Trends in the Vocational Training of Engineers [In Bulgarian]
Резюме. The successful professional realization of the engineers with additional teacher qualification is connected with identification and formation of key, basic, functional and ecological competencies. The article presents the results of an empirical survey with 32 employers from the thermal power plant “Maritza-Iztok†and 22 students from Technical University – Sofia, with additional professional qualification “Teacherâ€, about the significance of the competencies included in the panel of professional competence. The capabilities of inventions, planning and forecasting are listed as the most important skills of the prospective engineers. The ecological competencies are neglected by the respondents. The survey outlines the frames of the panel of professional competence. The results of the survey will provide opportunities for updating the engineering curricula in technical universities.
Keywords: competences, professional competence, job performance, psychological scaling
N. Ilieva, E. Boiadjieva
Влезте в системата, за да прочетете пълната статияTeaching Efficiency
Didactical Tools for Developing an Environmental Culture of Pupils in Chemistry in the Secondary School [In Bulgarian]
Резюме. This article shows the main didactic tools which help students in the secondary school to develop their environmental culture during their chemistry education. Appropriate classification of the problems in chemistry and environment learning and teaching is proposed. The criteria that would be satisfied when a testing learning is realized are described and commented. A sample test designed accordingly with these criteria is enclosed.
Keywords: ecological culture, didactical tools, environmental education, chemistry education
A. Angelacheva, E. Gergova
Влезте в системата, за да прочетете пълната статияExperiments
Polymetallic Complexes: CV. Synthesis, Spectral, Thermogravimetric, XTD, Molecular Modelling and Potential Antibacterial Properties of Tetrameric Complexes of Co(II), Ni(II), Cu(II), Zn(II), Cd(II) an
Резюме. Twelve complexes of Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) with two octadentate oxygen – nitrogen donor azodye ligands have been prepared. The characterization of the complexes has been made basing upon analytical, conductance, magnetic susceptibility, IR, electronic spectra ESR, NMR, thermo gravimetric, X-ray diffraction data and molecular modeling. The Co(II) and Ni(II) complexes are found to be octahedral, Cu(II) complexes are distorted octahedral and a tetrahedral stereochemistry has been attributed to Zn(II), Cd(II) and Hg(II) complexes. All the complexes are found to be tetrameric in nature. The antibacterial study of the ligands and some complexes against E.coli and S.aureus has been made.
Keywords: polymetallic complexes, tetrameric complexes, azodye complexes
Bipin B. Mahapatra, S.N. Dehury, A.K. Sarangi, S.N. Chaulia
Влезте в системата, за да прочетете пълната статияExperiments
Synthesis and Characterization of Mixed Ligand Cu(II) and Co(II) Complexes of L-Phenylalanine and Iminodiacetic Acid
Резюме. Mixed ligand complexes, Na[M{(C6H5 CH2 CH(NH2) COO)}{NH(CH2COO)2}.H2O], where M = Cu(II) and Co(II), formed with phenylalanine and iminodiacetic acid were synthesized and characterized by their elemental analysis, spectral (IR and UV) and magneto chemical studies. In both complexes, phenylalanine was found to act as a bidentate ligand coordinating through the carboxylate oxygen and the nitrogen atom of the amino group. The iminodiacetic acid, however, coordinated through the two carboxylate oxygen atoms and the nitrogen of the NH group, hence acted as a tridentate ligand. The remaining coordination position is satisfied by one water molecule. Thus both complexes have been suggested to show six fold octahedral structures.
Keywords: phenylalanine, iminodiacetic acid, Cu(II) and Co(II) complexes, synthesis, characterization, structure
G. Kumar, A. Munyaneza, G. Ditse
Влезте в системата, за да прочетете пълната статияAdvanced Science
Comparison of Properties of d-Element Compounds to Those of Compounds of s- and p-Elements with Similar Number of Valence Electrons [In Bulgarian]
Резюме. The d-block elements could be divided into three groups on the base of their electronic configuration at a given oxidation state. Properties of their compounds are compared to those of compounds of s- and p-elements with similar number of valence electrons. Zn2+ and Cd2+ compounds are close to Ca2+ and Sr2+ compounds but those of Hg2+ differ from Ba2+ compounds. Properties of all other d-elements with oxidation state of +2 are very different from those of alkali-earth metals. In this case, there are nonbonding electrons on d-orbitals of the d-element compounds. Mn2+ compounds make an exception: their properties are close to those of (Mg2+)Ca2+. They have five nonbonding electrons to generate a half-filled stable 3d-level. 2+- compounds of 4d- and 5d-elements form clusters. Properties of compounds of d-elements in which all available d-electrons take part are compared to similar compounds of p-elements. A significant difference is found between them. There are exceptions for Sc3+ compounds which are close to those of Al3+, and Mn7+ are similar to Cl7+ compounds. To be able to explain the role of d-orbitals it is necessary to have some additional knowledge.
Keywords: d- and p-elements, oxidation state, valence electrons, d-orbitals, clusters
E. Kirkova
Влезте в системата, за да прочетете пълната статияPersonalities in Science
Celebrating 90th Anniversary of Professor Elena Kirkova [In Bulgarian]
Резюме. Interview of Professor Adrian Tafrova-Grigorova, member of the Editorial Board of Chemistry: Bulgarian Journal of Science Education with Professor Elena Kirkova (Department of General and Inorganic Chemistry,University of Sofia)
Keywords: Professor E. Kirkova, 90th anniversary, Department of General and Inorganic Chemistry, University of Sofia
A. Tafrova-Grigorova
Влезте в системата, за да прочетете пълната статияHistory and Philosophy of Science
Second Principle of Thermodynamics: Why Are the Processes in Nature and Society Irreversible? [In Bulgarian]
Резюме. In this article two important questions are analyzed. What is the physical cause for the irreversibility of the processes in Nature? Why do processes in society have a direction? In both cases the interactions, conflicts, collisions between the entities of the systems are responsible for this fact. H-theorem of Boltzmann (1896) and Emerson’s ideas (1841) are considered in details. The author advocates the idea for more generality in school disciplines for closer and deeper understanding the laws that govern Nature and Society.
Keywords: irreversibility, second principle of thermodynamics, natural systems, social systems, H-function of Boltzmann, H-theorem of Boltzmann, Emerson
B. V. Toshev
Влезте в системата, за да прочетете пълната статияArchives
Teaching Science in the Bulgarian Schools for Girls: Geography (1897) [In Bulgarian]
B. V. Toshev (Ed.)
Влезте в системата, за да прочетете пълната статияForeign Educational Tradition
Science Literacy in the Former Yugoslavia: School Educational Programs on TV and Scientific-Popular Literature
Резюме. The policy of non-alignment (presided by the SFRY on the international level) caused the creation of a unique Yugoslav school system (schools and curricula), which was structurally neither Western nor Eastern (block) but rather a mixture of the both, simultaneously implemented in the Yugoslav model. The reform of the school system and the state education policy during the 60s and 70s of the 20th century influenced the formation of the Yugoslav school-educational and scientific TV program broadcasted by Yugoslav TV stations within a common TV program. Apart from educational documentaries of domestic production, educational shows of foreign production were also broadcasted, selected according to the teaching contents of the subjects of life sciences of the time (Physics, Chemistry and Biology) in primary and secondary schools. The shows from school program dealing with the teaching contents of Chemistry were broadcasted continuously from the late 70s to the mid 90s of the 20th century. They were filmed according to the curricula of the 7th and 8th grades of primary, and the 1st to 4th grades of secondary and grammar schools. An important contribution to the development and popularization of life sciences was made by children’s school program and numerous scientific-popular magazines (Politikin Zabavnik, Galaksija, and others) in Serbo-Croatian. The aim of this work is not only to present the development of school-educational TV program and its contents in the former Yugoslavia, but also to briefly describe the teaching of life sciences as a specific (endemic) Yugoslav TV phenomenon, as well as abundant foreign influence in the period from 1945 to the disintegration of SFRY (1991/92), little-known to general scientific public abroad.
Keywords: the former Yugoslavia (SFRY), life sciences, Chemistry, television, school-educational TV program, scientific-popular literature
M.D. Stojkovic
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