Electrometric determination of cu (ii) cations, Zn (ii) and Cr (iii) in aqueous, water-non-aqueous and mixed solutions

Аннотация

This work presents the results of the potentiometric determination of aqueous, non-aqueous and mixed solvents of copper (II), zinc (II) and chromium (III) cations: (propanol-2, acetone, methyl ethyl ketone, toluene, carbon tetrachloride, dimethylformamide) and their mixtures with water in a ratio of 1:1 and 1:19 by volume, the ratios of acid-base titrations are given. The quantitative results of the titration on a per kilote basis for the indicated cations Cu2+, Zn2+ and Cr3+ are based on the acidity constants of these cations assessed in the solvent environment specified above. The influence of the physical and chemical properties of solvents on acid-base titrations was studied. Due to the increase in the proportion of non-aqueous solvent in the solution, the dielectric constant of the solution decreases, and this leads to an increase in the ability to quantify acid-base titrations. Keywords: Potentiometry, metal cations, copper, zinc, chromium, dielectric constant, acidity constant. aprotic acids exhibit acidic properties of varying Introduction: It is known that heavy metal cations in strength. Of the above aprotic acids, copper and zinc solutions have their own acidic properties. Therefore, are dibasic acids, and chromium is a tribasic acid. they are also called aprotic acids or Lewis acids. The Taking into account the acidity of various solutions of acidic properties of metal ions depend on their position aprotic acids, methods of their acid-base in the periodic table, on the ionic charge and on the potentiometric titration can be recommended. In number of anions associated with the cation. The aqueous solution they are mainly titrated according to cations Cu2+, Zn2+ and Cr3+ are aprotic acids, which do the second acidity constant. The addition of non- not retain protons, and have wetting acidic properties aqueous water-miscible solvents to water improves the of varying strength in solutions depending on their ionic conditions for titration of aprotic acids. In this case, it charge. According to the literature, there are few works can be ensured that they can be titrated against all on their titrimetric acid-base determination. Given acidity constants. their acidic properties, ions can be titrated as acids in a mixed aqueous-non-aqueous solution. Because of this, METHODS we carried out their titrimetric analysis in non-aqueous The chosen objects were chlorides and sulfates of solvents mixed with water. It was of interest to aprotic acids of copper (II), zinc (II) and chromium (III). determine the content of aprotic acids, which play an Thus, ethanol, 2-propanol, acetone, methyl ethyl important role in the life of living organisms. To develop ketone, toluene, carbon tetrachloride, methods for the analysis of these aprotic acids, model dimethylformamide and their mixtures with water solutions of the substances under study were taken and were used as solvents. titrated based on acid-base reactions. As shown above, American Journal Of Biomedical Science & Pharmaceutical Innovation 29 https://theusajournals.com/index.php/ajbspi American Journal of Applied Science and Technology (ISSN: 2771-2745) During titration, solutions of potassium ethoxide and potential of the acid under study, мВ; Eo – half- 1/2 potassium propylites in ethanol and 1-propanol, as well as solutions of potassium acetate in suitable solvent titration potential of acid standard, мВ; 𝜃=58 media, were used as titrants. As a research method, we (above 200С) мВ or 𝜃=59 (above 250С) мВ. used potentiometric titration from electrochemical Benzoic acid was used as the standard acid. A analysis methods. To estimate pKa values, the hydrogen-selective electrode was used as an indicator Henderson method was used, based on potentiometric electrode, which was adjusted according to the method titration with glass hydrogen-selective and silver-silver attached to the pH meter using two buffer solutions (in chloride electrodes. The essence of the method is that, an aqueous solution). The reference electrode was a under the same conditions, two acids are titrated with silver chloride electrode filled with a saturated aqueous a strong alkali solution: one of them serves as a solution of doubly recrystallized potassium chloride. standard, and the second as the acid being studied. For