Kinetics of absorption of oxygen in aqueous solutions: (1) acidic chromous chloride, (2) acidic titanous chloride and (3) ammoniacal cuprous chloride

Abstract

The kinetics of absorption of oxygen in aqueous solutions of acidic chromous chloride and ammoniacal cuprous chloride were studied in a stirred cell. Both these reactions were found to be very fast and the theory of gas absorption accompanied by fast pseudo-m^th order reaction was used to analyse the results. The kinetics of absorption of oxygen in aqueous acidic solutions of titanous chloride were investigated in a bubble column where the reaction was found to be free from diffusional resistance. The reaction between oxygen and chromous chloride was found to be first order with respect to oxygen and second order with respect to chromous ion. The value of the third order rate constant for 2·0 M HCl solution was found to be 2·7 ×10¹² (cm³/g mole)² sec^-1 at 30°C. The oxidation of titanous chloride was observed to be zero order with respect to titanous ion and first order with respect to oxygen. The value of the first order rate constant was found to be 8·6 × 10^-3sec^-1. It has been suggested that in this case hydrolysis precedes the oxidation and it is likely that the reaction of oxygen with the hydrolysed product is the rate controlling step. The absorption of oxygen in aqueous ammoniacal cuprous chloride was found to be third order; first order with respect to each species, namely Cu⁺, oxygen and free ammonia. The value of the third order rate constant was found to be 7·5 × 10¹⁰ (cm³/g mole)² sec^-1. The higher value of the rate constant compared to that for oxidation of acidic solutions of curpous chloride indicates that the presence of a complexing agent such as ammonia increases the rate of absorption of oxygen substantially.