The Effects of Ionic Strength on Polytungstate Ions Equilibrium in KCl Solution

[摘要] The effects of ionic strength on the polynucleation reaction of tungstate ions and the protonized reaction of polytungstate ions have been investigated in the range of ionic strength from 1 M to 4 M KCl. The hexatungstate ions and the protonized forms of hexatungstate ions are formed in the tungstate solutions whose ionic strengths are 1 M to 4 M KCl. The equilibrium constants for the formation of hexatungstate ions and the protonized forms of hexatungstate ions are calculated in the range of ionic strength from 1 M to 4M KCl. The enthalpy changes for the formation of hexatungstate ions and the protonized forms of hexatungstate ions are as follows; 7H+ + 6WO42- = HW6O215- + 3H2O ¥ÄH¡Æ = -62.4¡¾0.6 H+ + HW6O215- = H2W6O214- ¥ÄH1¡Æ = -4.12¡¾0.10 H+ + H2W6O214- = H3W6O213- ¥ÄH2¡Æ = -4.36¡¾0.30 The free energy and entropy changes for the above reactions have been also calculated. A linear relation is formed between log K6,7 and ionic strength, and log k1 or log k2 vs.¥ì. log K6,7 = D¥ì + I where D = 1.66¡¾0.02 log k1 = D1¥ì + I1 where D1 = -8.065¡¾0.001 log k2 = D2¥ì + I2 where D2 = -0.376¡¾0.006

[学科分类] 化学（综合）