Electric conductivity of Cu (NO3) 2•3 Н2О solutions in dimethylsulfoxide
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Mamyrbekova Aigul Kumekbaevna, candidate of chemical science, associate professor, M. Auezov South Kazakhstan state university E-mail: aigul_akm@mail. ru Mamitova Aigul Dzhanabaevna, candidate of technical science, associate professor, M. Auezov South Kazakhstan state university Mamyrbekova Aizhan Kumekbaevna, candidate of chemical science, associate professor, A. Yasawi International kazakh-turkish university
Electric conductivity of Cu (NO3)23 Н2О solutions in
Abstract: Conductometric method studies electric conductivity of solutions crystalohydrate nitrate of copper Cu (NO3)2−3 H2 O in dimethylsulphoxide (DMSO) within the limits of concentration 0. 01−2. 82 M at 288−318 K electrodeposition are calculated limiting molar electrodeposition electrolit, limiting mobility of ions Cu2+ and NO3-, effective factors of diffusion of ions of copper (II) and nitrate-ions, a degree and a constant electrolytical dissociation at various temperatures.
Keywords: electrodeposition, dimethylsulphoxide, crystalohydrate of nitrate of copper (II), conductometry, electrolyte.
molecules are coordinated it is established experimentally [4, 3803], it means that in liquid DMSO units from 13 molecules are the steadiest. The superfluous negative charge of oxygen atom of the molecule (CH3)2SO causes formation of hydrogen bond with molecules of H2O, more stronger, than with methyl group of molecules DMSO. Formation of strong H-bonds is provedby the analysis of thermodynamic properties of system H2O-DMSO [5, 2240]. It is offered the following structures of het-eromolecular associates (CH3)2SO … H2O (1) and (CH3)2SO … H2O (2) appearing in binary system water — DMSO.
Really, from dimethylsulfoxide solution of copper nitrate the qualitative copper coverings are received [6, 1165]. High solubility of copper nitrate crystallohydrate Cu (NO3)2−3H2O in DMSO is established [7, 416].
In work the results of research of Cu (NO3)2'-3H2O solution electric conductivity in DMSO in the range of temperatures 288−318 K is described. Conductivity of solutions was measured by conductometer OK-102/1. Electrodes made from the platinized platinum are rigidly fixed on the certain distance. The constant of conductometric
The water solution of copper (II) nitrate acidified by nitric acid is of interest as electrolyte of coppering, carried out at the raised density (till 100 A-dm-2). The received coverings do not contain nonmetal-lic inclusions and are characterized by low resistance [1, 64]. For complicating of parallel restoration of nitrate-ions harmfullyEinfluencing on extraction of metal it is offered to introduce in nitrate electrolyte chlorides-ions, various buffer, surface-active and other additives [2, 50].
In spite of the fact that it is marked in literature the high solubility of nitrate salts of many metals in dimethylsulfoxide (DMSO), solubility of anhydrous copper (II) nitrate in DMSO is not studied.
DMSO is bipolar aprotonic solvent adsorbed on a surface of metals by positive end, through the atom of sulphur. In liquid DMSO in usual conditions (lower than 40 °C) molecules of (CH3)2SO are bonded in dimeric polymers, in which basis four-nuclear cycles [3, 380−395].
Taking place weak interaction of hydrogen atoms of methyl groups with oxygen of the nearest next molecule complicates occurrence of long molecular bonds. Nevertheless in formed homomolecular associates round each molecule of DMSO 12 other
cells was determined by 0.1 M KCl. The cell with the studied solution was thermostated with accuracy 0.5 °C by ultrathermostat UTU-4. Used in work crystallohydrate was synthesized from a copper wire and was cleared by recrystallization from a water solution. Chemically pure DMSO was exposed to vacuum distillation (nD25 = 1. 4816).
Electric conductivity of Cu (NO3)2'-3H20 solutions in DMSO quickly increases at temperature 288 K with growth of the salt content in a solution till 0.4 M. The further increase of copper nitrate tri-hydrate solution concentration in DMSO leads to gradual decrease of electric conductivity till some limiting value. At the raised concentration (above 1. 4) reproducibility of measurements decreases.
With increase of temperature till 318 K mobility of electrolyte ions is accelerated and conductivity of solutions increases. At 318 K disorder of experiment points extends in area oflower concentration that is explained by destruction of the intermolecular hydrogen bonds appearing at low temperatures between molecules (CH3)2S0 and H2O, introduced in structure of crystallohydrate.
Dependence of molar electric conductivity A [½Cu (N03)2−3H20, DMSO, T] of studied solutions from concentration in the diluted solutions (till 0.5 M) is kept in with the parabolic law of Kol-raush-Onzager.
With temperature growth the inclination of line section increases and simultaneously the disorder of experimental points strengthens. On values of electric conductivity by a method of Fuoss and Krauss [8, 125−130] the values of limiting molar electric conductivity are established and association constants in investigated solutions are calculated. Temperature increase causes decrease of size of relative temperature coefficient of electric conductivity of dimethylsulfoxide solution of copper salt eA° = (3lnA0/3T)c. Such dependence of temperature factor of electric conductivity, marked by Valden [9, 602], testifies to viscosity imposing, as essential factor of mobility of ions.
Certain interest has the dependence of relative temperature factor of electric conductivity of investigated systems from concentration of solution. In diluted (lower than 0.3 M) solutions of copper
nitrate in DMSO the average size of temperature factor of electric conductivity with in temperatures 288−308 K of the same order as eAo is 0. 0216 K-1. And at temperatures 308−318 K it is lower or equal to 0. 0190 K-1. With increase of the content of copper salt in solution eA increases by a curve that is connected with strengthening of interaction of solution components and aggregation of received products. Maxima on the diagram of dependence of relative temperature factor of electric conductivity from structure indicate the chemical interaction of components, and their abscissas correspond to structure of connections formed in solution.
The first and second maxima correspond the following parities of molar share of components [Cu (NO3)2]: [H20]: [(CH3)2SO] = 1: 3:28 and 1: 3:14 accordingly. The existence of steady homo-molecular units from 13 molecules (CH3)2SO in liquid DMSO was mentioned above. From the received parities it follows that in formed adducts of the first maximum on mole of crystallohydrate Cu (NO3)2−3H20 it is necessary two associates of DMSO, in more concentrated solution (0.9 M) one associate.
Continuing hypothetical, based on e, C — dependences, in conclusion, it is possible to assume that in process of increase of copper salt content in a solution large units on a basis of homomolecu-lar associates of DMSO are decomposed, forming solvated ions of usual type and heteromolecular associates of water with DMSO. Solvated ions and heteromolecular associatesare united with molecules of DMSO in process of increase of solution concentration. Simultaneously in solution the possibility of ionic association owing to electrostatic adhesion of cations and anions of electrolyte appears and strengthens. There is aggregation and agglomeration of particles in solution, causing observed in experiment increase of temperature factor of conductivity of investigated solutions. Maximum is more expressed in the diluted solutions (0. 47 M) when homomolecular associates in DMSO prevail. The maximum is more indistinct at concentration 0. 94 M and disappears absolutely in more concentrated solutions when homomolecular associates are destroyed and the increasing role the products
of interionic interactions and heteromolecular associates play. Increase of temperature factor with growth of concentration is caused also by increase of solutions viscosity.
On values of limiting molar electric conductivity and mobility of ions of NO3- in DMSO (NO3-, DMSO, 298 K) =27.0 S-cm2-mole-1 on the basis of independence of ions movement of Kolraush the mobility of copper (II) ions in DMSO are calculated. Calculations of (NO3& quot-) and (½ Cu2+) at various temperatures are made, accepting temperature factors of conductivity of ions equal to temperature factor of conductivity of electrolyte.
In DMSO the mobility of Cu (II) ions is higher than mobility of NO3- ions. At the same time the parity of mobility of Cu2 + and NO3- ions in water is reverse according to the observed one in DMSO. In water solutions mobility of copper (II) ions is rather higher than in the organic medium. These phenomena are explained by stronger solvation of copper (II) ions in DMSO and the raised viscosity of solutions.
In pure DMSO the solvent molecules at room temperatures form steady enough units with 13 molecules. Homomolecular associates of DMSO are linked poorly and consequently the solvent possesses poor expressed that is broken at temperatures about 318 K. Small quantity of copper nitrate crystallohydrate dissolving in DMSO, are dissociated completely. Thus electrolyte components are connected mainly with mentioned multi-molecular units DMSO, forming complexes of type Cu (DMSO)62+ or [Cu (DMSO)4 (H2 O)2]2+, and molecules H2O form stable solvates H2O… (H3 C)2SO. With increase of salt concentration the share of molecules of the solvent on one ion in solution decreases. Deficiency of mol-
ecules for ions increases because of increase of electrolyte content and molecules of water, being introduced with crystallohydrate. Water molecules contacting with molecules (H3 C)2SO by hydrogen bonds, cause disintegration of homomolecular associates of the organic nature and, forming stronger heteromolecular associates cause strengthening of structuring and, as consequence, increase of viscosity of solution. In process of increase of concentration of DMSO decreases solvation number of Cu2+ and probably, of NO3-. As a result of action of these two factors solvation of ions decreases and viscosity of solution increases and at 288 K in 0.4 M solution association of ions of electrolyte gets appreciable value, preventing the diffusion of ions and work of conductivity of solution. The further increase of concentration of electrolyte is accompanied by increasing of electric conductivity. Increasing of temperature causes the general increase of mobility of ions and conductivity of solution at the expense of increase of diffusion speed and migration of ions, and also displacement of electric conductivity maximum to a higher concentration. At higher temperatures (308−318 K) the mentioned heteromolecular associates are decomposed and viscosity decreases.
Thus, crystallohydrate of copper (II) nitrate is well dissolved in dimethylsulfoxide in a wide interval of concentrations (we test solutions with concentrations till 2.8 M of Cu (NO3)2−3H2O) and temperatures 288−318 K. Electric conductivity of solutions depending on concentration submits to known laws. The maximum electric conductivity is observed in 0.4 M solution of copper (II) nitrate trihydrate in DMSO at T=288 K which is displaced to higher concentration at the raised temperatures.
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