KINETIC STUDIES OF THE OXYGEN EXCHANGE OF CHROMATE AND ARSENATE IONS WITH WATER. CATALYSIS BY TELLURATE AND TELLURITE IONS

The oxygen exchange reaction of the chromate ions with water is catalyzed by the tellurate and tellurite ions. The catalytic reaction rate (RC), which is defined as the increase in the rate of the chromate-oxygen exchange upon the addition of Te(VI) or Te(IV), was studied by an 18O tracer method. The catalytic process has been interpreted in terms of the rapid reversible condensation of the Cr(VI) with Te(VI) or Te(IV) species to form hetero-poly anions. As exemplified for the Cr(VI)–Te(VI) reaction system, the rate law is given as the sum of kinetic terms: RC = ∑kij[Cr(VI)]i × [Te(VI)]j where [Cr(VI)]i and [Te(VI)]j denote the concentration of the various ionic species of the chromate and tellurate ions, respectively, and kij is the rate constant of the elementary reaction between (Cr(VI))i and (Te(VI))j. The catalytic rates were analyzed according to the rate law in order to obtain the rate constants kij. The catalytic reaction system As(V)–Te(IV) was also studied. The values of kij obtained for various...