The Determination of the Activity Coefficients of Pb(II), Cd(II), and Zn(II) Chlorides in N,N′-Dimethylformamide by Means of Electromotive-force Measurements of the M(Hg)/MCl2(DMF)/AgCl; Cells

Abstract

Abstract Electromotive-forces have been measured for the cells of the M(Hg)/MCl2(DMF)/AgCl;Ag type at 25.00±0.01 °C, where M are Pb, Cd, and Zn metals and were M(Hg) are amalgams saturated with these metals. The standard potentials of the corresponding metals relative to the silver-silver chloride have been determined, and the mean activity coefficients and the standard free-energies of formation have been calculated for the solvated salts of PbCl2, CdCl2, and ZnCl2 from the electromotive-foce data. Experimental works were carried out by using an H-shaped Pyrex glass cell which was coated externally with silicon grease to eliminate electrical leakage from the water bath. The electromotive-force measurements were made with a digital voltmeter, the voltage sensitivity and the input impedance of which were 10 μV and 100 megohms respectively. The standard potentials for the cells of the M/MCl2(DMF)/AgCl;Ag type were 0.3271 for PbCl2, 0.5762 V for CdCl2 and 0.8986 V for ZnCl2.