The second dissociation constant of carbonic acid in ethanol–water mixture from 5°C to 45°C

Abstract

The determination of the second dissociation constant of carbonic acid in 5, 15 and 25 mass% ethanol–water mixed solvents has been made with a cell of the type: Pt, H 2 (101.325 kPa) |NaHCO 3 ( m 1), Na 2CO 3 ( m 2), NaCl ( m 3), X mass% ethanol+Water| AgCl–Ag at 278.15–318.15 K. The dependence of p K 2 on temperature is given by p K 2= A 1+ A 2/ T+ A 3 T. According to thermodynamic relationship and above equation, the thermodynamic quantities for the dissociation process were determined. The dependence of p K 2 on the dielectric constant of mixed solvent is discussed in terms of Beveradge model.