Electrical conductivities of aqueous ZnSO4?H2SO4 solutions

Abstract

Conductivities of aqueous ZnSO4−H2SO4 solutions are reported for a wide range of ZnSO4 and H2SO4 concentrations (ZnSO4 concentrations of 0∼1.2 M and H2SO4 concentrations of 0∼2 M) at 25°C, 40°C and 60°C. The results indicate that the solution conductivity at a given ZnSO4 concentration is controlled by the H2SO4 (H+) concentration. The variation of the specific conductivity with ZnSO4 concentration is complex, and depends on the H2SO4 concentration. At H2SO4 concentrations lower than about 0.25 M, the addition of ZnSO4 increases the solution conductivity, likely because the added Zn2+ and SO 4 2− ions increase the total number of conducting ions. However, at H2SO4 concentrations higher than about 0.25 M, the solution conductivity decreases upon the addition of ZnSO4. This behaviour is attributed to decreases in the amount of free water (through solvation effects) upon the addition of ZnSO4, which in turn lowers the Grotthus-type conduction of the H+ ions. At H2SO4 concentrations of about 0.25 M, the addition of ZnSO4 does not appreciably affect the solution conductivity, possibly because the effects of increasing concentrations of Zn2+ and SO 4 2− ions are balanced by decreases in Grotthus conduction.