Letters to the Editor
On the Use of Uniform Conceptional Terms in Education and Learnimg
A.A. Panaiotov
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Kp Does Not Play the Role of the Thermodynamic Equilibrium Constant, Ko: A Discussed Example of General Chemistry Tectbooks’Misrepresentations
Absract. Equilibrium constants are important quantities when dealing with chemical equilibrium. Many first-year chemistry textbook authors do not define these terms accurately and confusion arises when reporting them. On this regard, this research discusses a common erroneous treatment performed on the teaching equilibrium constants as many textbook authors assume that the practical equilibrium constant Kp plays the role of the thermodynamic equilibrium constant, Kº. Thus, many authors also state that Kp is a unitless quantity. Hence, after documenting a particular case that exemplifies some widespread terminological misrepresentations related to the handling of the equilibrium constants, which prompts to reviewing the proper definition of each of the terms analysed, one example is presented in order to illustrate the correct treatment of the quantities involved. This analysis may help in the discussion and clarification of the misleading conventions and assumptions reported in this study.
Keywords: equilibrium, misrepresentations, textbooks, thermodynamics
J. Quilez
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Why Solids and Pure Liquids Are Not Part of Equilibrium Expression
Absract. The article deals with the expression of equilibrium constant of a reaction that might include a solid or a pure liquid as a reactant or a product. The typical textbook explanation for excluding terms relating to solids and pure liquid is that their concentrations are constant and so need not be included. This need would not arise if the equilibrium constant were written in terms of activities rather than concentrations or pressures, but the concept of activities is not covered that early in a typical undergraduate syllabus. In this article the concept of Gibbs energy is used to explain why the equilibrium constant is written as it is.
Keywords: equilibrium constant; heterogeneous equilibrium; Gibbs energy
J. Ahmad
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Blended Learning Tasks for Teaching English as a Foreign Language Methodology Course (For Students of Biology) [In Bulgarian]
Absract. The article is dedicated to tasks designed for the discipline Teaching English as a Foreign Language& Practice for the binary specialty Biology and English, Faculty of Biology, Sofia University “St. Kliment Ohridskiâ€. The focus is on optimization of the face-to-face classes by introducing blended learning tasks. An informed choice of relevant technology is proposed for each element of the task. The specifics of tasks for binary specialties is considered by identifying the similarities between the two different areas: teaching a foreign language and teaching science.
Keywords: blended learning tasks, dual teacher training, teaching Biology in English
A. Kremenska
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Conversion of the Teaching in Astronomy into a Real Research Process – An Innovation in the Teaching Practice [In Bulgarian]
Absract. This article describes the principles of a new European educational practice: Inquiry-Based Learning in the astronomy education. We present the results from such education of pupils from the study circle in astronomy of the Public Observatory, Varna. The discoveries of new asteroids as well as the study of Supernovae and Novae in the framework of real scientific process provoked their interest for acquisition of deep and sustain knowledge as well as motivated them to future realization in the field of natural sciences.
Keywords: inquiry-based learning, interactive educational methods, astronomical observations, аsteroids, Novae, Supernovaе
V. Radeva, D. Kyurkchieva, D. Dimitrov, G. Borisob
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Synthesis and Characterization of Palladium Complexes of Some N,N,N’,N’-Tetrakis(2-Pyridyl-Methyl) Alkanediamine Ligands
Absract. The syntheses and characterization of complexes formed from the reaction of bis(acetonitrile)palladium(II) chloride, (CH3CN)2PdCl2 , with nitrogen-based ligands of the type N,N,N´,N´-tetrakis(2-pyridylmethyl)alkanediamine {alkane= butane (L1), hexane (L2) and octane (L3)} were investigated. Ligand to metal (L:M) ratios of 1:1 and 1:2 were employed in the preparation of the palladium complexes. L1 reacted with (CH3CN)2PdCl2 in methanol and at a ligand to metal ratio of 1:1 to yield a cream white complex (A). Each of the three ligands (L1, L2, L3) reacted with (CH3CN)2PdCl2 at a ligand to metal ratio of 1:2 in HCl medium for 24 hours yielding light yellow powders B, C, and D, respectively. Results from IR, 1H-NMR and Mass spectroscopic techniques combined with elemental analyses suggest a mononuclear complex for A and dinuclear complexes for B, C, and D.
Keywords: synthesis, 2-pyridylmethyl, ligands, palladium, complexes
O.A. Oyetunji, F.M. Nareetsile, R. Gontse, L. Sheling
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A New Approach for the Synthesis of p-Anisyl Ethyl Fumarate: A C-9154 Antibiotic Analogue
Absract. A simple, energy–efficient, and relatively quick synthetic procedure for the synthesis of p-anisyl ethyl fumarate from p-anisaldehyde has been carried out. The synthesis was started by solvent-free reduction of the aldehyde using sodium borohydrate. The second step was solvent-free condensation of the resulting alcohol with maleic anhydride to be followed by esterification of the resulting acid with ethanol in the presence of benzenesulfonic acid as the catalyst. Satisfactorily isolated yields (65-98%) were achieved confirming that the preparation of the C-9154 antibiotic analogue is possible in sustainable fashion.
Keywords: p-anisaldehyde, p-anisyl ethyl fumarate, C-9154 antibiotic, solvent-free
M. Firdaus, A. Ainurofiq, A. Vellarani
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DDT – The Substance Which Was Considered as Salvation and Today It Can Be Found in the List of Forbidden for Use Substances [In Bulgarian]
Absract. The history of discovery of DDT (dichlorodiphenyltrichloroethane) is described in the present article. The insecticide DDT was broadly used in agriculture, medicine and human life. However, in our days, this substance is in the list of forbidden for using substances.
Keywords: DDT, insecticides, forbidden substances
I. Kuleff
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The Effect of KOH and KCl Addition to the Destilation of Ethanol-Water Mixture
Absract. This paper discuss the addition of KOH and KCl to the destilation of ethanol-water mixture. The investigation were on the azeotrope point in destilation curve, the yield of ethanol as the destilation product, and also on colligative and thermodynamic properties. Meanwhile, the thermodynamics parameters were the change on Gibbs energy of mixing, ΔGmix , the entropy of mixing, ΔSmix and the evaporation enthalpy of mixture, ΔHvap. The result shows that the addition of electrolyte KOH and KCl eliminated azeotropic point as it is described in T-x distillation curve. In addition, the ethanol yield increased, the Gibbs energy of mixing, ΔGmix, reduced, that indicates the mixing process occurred spontaneously. The spontaneity is also supported by the value of the entropy of mixing, ΔSmix, which is positive. It refers to the increasing of irregularity, confirming the spontaneity of mixing process. Meanwhile, the enthalpy of evaporation, ΔHvap, of ethanol-water mixture 300.1105 kJ/mol. The enthalpy increase to 738.4329 kJ/mol when KOH was added and the enthalpy value is 340.2338 kJ/mol when KCl was added. It indicates that water as main component in the mixture became more difficult to vaporize and it allowed the ethanol molecules to be freely released during destillation.
Keywords: azeotrope, colligative properties, distillation, addition of electrolyte, ethanol-water, thermodynamic properties
K.D. Nugrahaningtyas, F. Rahmawati, A. Kumalasari,
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Prof. Widen Tabakoff (1919-2015) – A Course of Life and Scientific Achievements [In Bulgarian]
Absract. This paper is in commemoration of the recently passed away prof. Widen Tabakoff (1919-2015), USA. Widen Tabakoff was born in 1919 in Stakevtsi, near Belogradchik, Bulgaria. He was a famous airspace engineer and researcher who participated in NASA program “Apolo†for sending people to the Moon.
Keywords: Widen Tabakoff, aerospace engineering, material science, Apolo
B.V. Toshev
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The First Years of Physical Chemistry in Bulgaria [In Bulgarian]
Absract. The famous Bulgarian physicochemical school of Stranski, Kaishev and their associates and disciples has been developing on the basis of the Department of Physical Chemistry at Sofia University „St. Kliment Ohridski „. This University unit was occupied by Dr. Iwan Stranski in 1926. This article describes the early history of physical chemistry in Bulgaria with the creation of the Department of Physical Chemistry, the inaugural lecture of Dr. Stransky, the academic staff, academic activities, the first scientific publications and training of PhD students. The public recognition and international prestige of the Department of Physical Chemistry are both in the focus in this paper as well.
Keywords: University of Sofia, physical chemistry, Iwan Stranski
B. V. Toshev
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Teachers in Learning with Using of Information and Communication Technologies [In Bulgarian]
Absract. In the article is presented author’s viewpoint about the functions and activities of teachers in learning with using information and communication technologies. The results of a proper educational experiment on this topic are presented.
Keuwords: information and communication technologies, teachers, secondary education, physics teaching.
G. Kalpachka
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