inorganic chemistry

Priyamstudycentre.com, 2021

Manganese (Mn), chemical element, a greyish-white hard, brittle paramagnetic metal of Group 7 (VIIB) of the periodic table used mainly as an additive to steel. The Swedish chemist Bergmann discovered the presence of magnesium in the black magnesia but fails to isolate it. In chemistry, the element was isolated by another Swedish chemist Johan Gottlieb Gahn and studies by the Swedish chemist Carl Wilhelm Scheele in 1774. At first, the metal was named in Latin word magnesium from the old name pyrolusite but in 1808, the Latin name of manganese changed to manganism to avoid confusion.

Plant and Soil, 1969

Nature, 2007

In these chapters some of the features which are charac- teristic of every chemical phenomenon are sought out, put into words, and illustrated. V PREFACE No conception is defined, and no generalization or law is developed, until such a point has been reached that applications of the conception and experimental illustrations, later to be related in the law, have already been encountered, and there is about to be occasion for further applications and illustrations of the same things in the chapters immediately succeeding. In these chapters the applications are frequent and explicit. Later, page references in parentheses con- tinue to indicate the recurrence of examples which might other- wise fail to be noticed. It is one thing to come to know a principle of the science, and quite another thing to have acquired, by constant repetition of the process, a confirmed habit of using the prin- ciple on every appropriate occasion. To assist still further in the attainment of this end, an attempt is made in the last six chapters again to mention and illustrate, by way of review, the most important principles of the science. No conception or principle is given at all, unless, in its most elemen- tary aspects, it can be made clear to a beginner ; and unless it is capable of numerous applications in elementary work; and, finally, unless a knowledge of it is of material use in organizing and unifying the result of such elementary work. An attempt has been made to state the laws and to define the conceptions of the science in terms of experimental facts. The figurative language of hypothesis has been employed only in explanations. Familiarity with physical conceptions and facts is so indispensable to the chemist that no apology is needed for the rather full treatment which some of them have received. No two chemists would agree perfectly in regard to the apportion- ment of space. The processes of chemical industiy, and the every-day applications of chemical science, cannot all be mentioned. These fields, and that of mineralogy, can be represented by examples, with- out the incompleteness of the result being in any way a detriment to a work of a general character. Again, a dense array of descriptive material, unillumined by explanation, is a positive injury to an intro- ductory treatise. All reference to historical matters cannot be omitted, but a logical display of the subject can be achieved with comparatively PREFACE yii little of the history. Of all the aspects of the science, the theoretical is thus the one whose treatment is susceptible of least abbreviation. The principles of chemical equilibrium are (and have been for the past half -century) fully as much required for intelligent consideration of the simplest experiment, as is the theory of combining proportions itself. Important parts of the theories of solutions and of the battery are much more recent, but each is equally indispensable to the under- standing of matters which cannot long be withheld from the notice of the beginner. Surely space ought not to be saved by entire omission of essential parts of the chief thing that makes chemistry at all worthy of a place amongst the sciences. Nor may we attain brevity, no matter how great the temptation, by condensing the passages on theory until they reach the limit of comprehensibility by an expert. Without clear exposition, full illustration, and frequent application, laws and princi- ples simply repel, or worse still, mislead the beginner. We reach the same conclusion from another view-point. Every student should have access to, and should use, reference books devoted especially to descriptive, industrial, historical, and physical chemistry, and to mineralogy and crystallographyat least one good book in each of these five subjects. With the help of the index, the veriest tyro can find in a few moments, almost anything he wants in four out of five of these branches. But just the opposite is the case with the theory. Only an expert realizes what information he is in need of, and knows under what titles to look for it. And often even the expert would fail to understand the isolated sentence or paragraph when found. In a large proportion of connections the beginner sim- ply cannot use such a book for rapid reference at all. In many lines, therefore, much may be left to outside reading, but for theory almost* no dependence can be placed on reference work in other books. For the reasons enumerated above, an unusually large proportion of space has been given to theoretical matters. The actual amount of theory is no greater than is usual in books of the same class, but the explanations are often fuller. Even so, the beginner will probably find that some parts form reading as stiff as any he is accustomed to undertake, without complaint, in physics or mathematics. It can only Viil PREFACE be said that easily read modes of presenting the science of chemistry are apt to dehide the l)eginner into thinking he has mastered the sub- ject, when in reality he has simply been steered clear of the chief diffi- culties. The order of topics was determined by many considerations, jointly. For example, in the first week of his work, a student may encounter experiments, in connection with which, almost every part of chemical theory might usefully be discussed. But mastery of the theory must necessarily come bit by bit, and the theory is therefore distributed through the book. Instead of being introduced as soon as a fragment offers a chance for explanation, the treatment of each of the various theoretical subjects, as far as possible, has been postponed until a whole chapter could be devoted to it. The result makes subsequent reference easier, and facilitates alterations in the order of study. Thus, the hypothesis of ions is not mentioned as soon as it well might be, because satisfactory treatment of it must follow the molecular and atomic hypotheses of which it is an extension, and because the full explanation of this hypothesis must be preceded by some account of the phenomena of electrolysis and of the essential properties of solutions, and, also, by a discussion of chemical equilibrium, a subject which of necessity presupposes two or three months' work in chemistry. There is another disadvantage which arises from a premature explanation of the hypothesis of ionization. When it appears at an early stage, too long an interval separates this subject from the study of the metallic elements, and the details are largely forgotten before the field for their chief employment is reached. The paragraphs in smaller type are not intended for beginners, but *for advanced students and teachers, which accounts for the fact that reference will frequently be found in them to subjects treated system- atically in later chapters. The exercises and problems are simply samples of some of the various kinds of questions which might be raised in dozens at the end of every chapter. Recent works on general chemistry have been consulted during the revision of the manuscript. Of these A. A. Noyes' admirable General PREFACE ix Principles, Ostwald's Grundliniena veritable tour de force, and Blox- ani's Chemistry may be mentioned as having proved most suggestive. The author owes special thanks to several friends who have undertaken the toilsome work of reading part or all of the book in manuscript or in proof, and in particular to his colleagues Messrs.

Mononuclear, binuclear Ni II and heterobinuclear Zn II Ni II complexes have been derived from lateral macrobicyclic tricompartmental ligands embracing three different donor sets: (i) O 2 N 2 -donor set, derived from ether oxygens and tertiary amine nitrogens; (ii) N 2 O 2 -donor set, derived from tertiary amine nitrogens and phenolic oxygens; (iii) O 2 N 2 -donor set, derived from phenolic oxygens and azomethine nitrogens. Cyclic voltammograms of the mononuclear Ni II complexes showed irreversible one-electron reduction processes in the )1.2 to )1.3 V region and an irreversible oxidation process in the range +0.8 V potential region. The binuclear complexes showed quasireversible two-step single electron reduction processes around the )1.3 and )1.7 V potential regions. The anodic potential region showed an irreversible oxidation process at +1.0 V. The heterobinuclear Zn II Ni II complex showed an irreversible reduction of the Ni II species at )1.55 V. The catalytic hydrolysis towards 4-nitrophenyl phosphate by the mononuclear, binuclear Ni II complexes and the heterobinuclear complex were found to be appreciable. The pseudo-first order rate constant for the catalytic hydrolysis catalyzed by the binuclear and heterobinuclear complexes were found to be higher (9.8 · 10 )4 s )1 ) than that of the corresponding mononuclear complexes (1.3 · 10 )5 s )1 ), which ascertain the requirement of two metal ions in close proximity for the binding of the nucleophilic OH and the phosphate group.

Thermochimica Acta, 2009

In this work the reaction between several manganese oxides and chlorine is investigated. The reaction path for the chlorination of the oxides is established, which involves recrystallization of high valence manganese oxides: Mn 3 O 4 and Mn 2 O 3 during the chlorination of MnO, and Mn 2 O 3 during the chlorination of Mn 3 O 4 and Mn 2 O 3. The starting temperature for the reaction of the oxides is determined by non-isothermal thermogravimetric measurements. Analysis of the samples at different reaction degrees reveals that three simultaneous processes are taking place during the whole reaction: chlorination, volatilization of manganese chloride and recrystallization of manganese oxides. The effect of temperature in the reaction rate is analyzed. The activation energies obtained for the reaction of the three oxides with chlorine, which are in accordance with the vaporization enthalpy of MnCl 2 , suggest that although during the mass loss three processes occur (chlorination, recrystallization and volatilization), volatilization of manganese chloride has a strong influence in the rate observed.

2014

COMPREHENSIVE QUESTIONS Q1) Design a selective two-step synthesis for cis-and trans-[Pt(NH 3)(PMe 3)Cl 2 ] starting with PtCl 4 2-. Q2) [Cu(NH 3) 4 ] + is completely colorless while [Cu(NH 3) 4] 2+ is intensely blue. Explain this observation using appropriate drawings.