MECHANISM OF ELECTRO REDUCTION OF CHROMIC ION AT THE MERCURY CATHODE

摘要

The mechanism of reduction for chromium (Ⅲ) ion to chromium (Ⅱ) at the mercury cathode was studied in 0.1M. KNO3. Data obtained at varying temperature and solution composition from polarograms gave values for H, S, and F which indicated that two mechanisms were involved. At potentials more positive than the polarographic half-wave potential the mechanism appeared to be simple electron transfer from the electrode to the chromium (Ⅲ) ion in solution. When the potential was more negative than the half-wave potential electron exchange between the reduced chromium ion near the electrode surface and a chromium (Ⅲ) ion in solution became appreciable Values for the heat of activation for the reduction of chromium (Ⅲ) to chromium (Ⅱ) in 0.1M KNOo for the electron transfer and exchange reaction mechanisms were determined to be 34.7 and 27.0 kcal mole-1 , respectively