Free Energy Change For Formation Research Articles

Chelate Formation between Molybdenum (VI) and Sodium Alizarin 3‐sulphonate; Studies on the Composition and Stability of the Chelate

AbstractThe composition of the red coloured molybdenum(VI) –(Alizarin Red S) chelate (γmax 470 mμ), determined by continuous variations method, the slope ratio method and the mole ratio method, comes out to be 1:2. The chelate is stable between pH 2.5 and 6.0. The value of log K is 9.2 ± 0.1, the free energy change of formation at pH 3.5 ± 0.2, ionic strength 0.1 M (NaClO4) and 25°C, being −12.6 ± 0.1 K Cals./mole.

Composition and Stability of the Chelate between Aluminium (III) and sulpho‐dichloro hydroxy‐dimethyl fuchson dicarboxylic acid (trisodium salt) and analytical applications of the reaction

AbstractThe reaction of sulpho‐dichloro hydroxy‐dimethyl fuchson dicarboxylic acid (trisodium salt) with aluminium (III) ions in aqueous solution to give a stable violet complex has been studied in detail, regarding the composition and stability of the chelate and its analytical applications. Absorbance as well as electrical conductance measurements have been performed to determine the composition of the chelate which comes out to be 1:1 (metal:chelating agent). The chelate has its maximum absorbance at 545 mμ, and is stable between pH 3.05 and 6.60. The system obeys Beer's Law over a concentration range of 0.013 to 0.980 p. p. m. of aluminium. The value of log K, as calculated by the absorbance data is 4.3 ± 0.1 at pH 4.0 ± 0.2, temperature 30°C and ionic strength 0.2 (KCl). The corresponding free energy change of formation has also been evaluated. The effects of pH, temperature, time and diverse ions on the reaction have been studied and suggestions have been advanced on the possible position of the chelate ring in the complex. A procedure for the colorimetric microdetermination of aluminium has also been suggested.

Composition and Stability of the Chelate between Uranium(VI) and Sulfodichlorohydroxydimethyl Fuchson Dicarboxylic Acid(Trisodium Salt)

The composition and stability of the uranyl Chrome Azurol S chelate are reported. It was found that the reagent behaves as a colloidal electrolyte. Color formation was observed to be immediate and the absorbance values remained constant at least up to 72 hr. Continuous variation curves at 570 and 585 m mu confirmed the stoichtometry as one UO/sub 2/(II) to one Chrome Azurol S. The value of the apparent stability constant for the 1: 1 chelate at a pH of 5.0 and temperature of 30 deg C was 4.5 plus or minus 0.1 and 4.9 plus or minus 0.1 depending on the method. The corresponding free energy change of formation was - 6.2, 0.1 and -6.8 = 0.1 kcal, respectively, at 30 deg C. Suggestions are given as to the structure of the chelate. (P.C.H.)

Thermodynamic Studies on Cobalt Complexes. II. Solubility and Standard Free Energy of Formation of [CoA6]-type Salts

Abstract The solubilities of hexamminecobalt(III) chloride, bromide, nitrate and perchlorate were measured at 10∼35°C. From the solubility measurements the relationships between the equilibrium constant of the solution and the temperature were calculated. The heats of solution calculated from these data agreed approximately with the values given in the literature and those calculated by using formulae of Kapustinski\v{i} and Fajans. The free energy changes of formation of these complexes in the solid state were calculated for the first time. It is concluded from the results that the stability of these salts decreases in the following order: & [Co(NH_3)_6]Cl_3>[Co(NH_3)_6](NO_3)_3> & [Co(NH_3)_6]Br_3>[Co(NH_3)_6](ClO_4)_3