engleski

Standard Potentials of Silver-Silver Bromide Electrode and Related Thermodynamic Quantities in 2-Propanol-Water Mixtures

The standard potentials (E^o_m) of silver-silver bromide electrode in 2-propanol-water mixtures (containing 30, 50, 70 and 90 wt-% 2-propanol) have been determined at 15, 25 and 35 ^oC using a cell of the type Pt(Pd), H_2(g) / HBr(m), x wt-% 2-propanol-water mixture / AgBr, Ag with m in the range from 0.003 to 0.1 mol kg^-1. Values of Eom varied with temperature in each solvent according to equations a) 30 wt-% 2-propanol: E^o_m/V = 0.05720 - 5.50*10^(-4) (t - 25) - 6.15*10^(-6) (t - 25)^2 b) 50 wt-% 2-propanol: E^o_m/V = 0.04023 - 8.49*10^(-4) (t - 25) - 4.50*10^(-6) (t - 25)^2 c) 70 wt-% 2-propanol: E^o_m/V = 0.00575 - 12.37*10^(-4) (t - 25) - 5.95*10^(-6) (t - 25)^2 d) 90 wt-% 2-propanol: E^o_m/V = - 0.0764 - 20.55*10^(-4) (t - 25) - 13.5*10^(-6) (t - 25)^2 These values have been used to calculate 1) standard thermodynamic quantities for cell reaction and the reaction involving HBr formation, 2) mean activity coefficients of HBr, 3) the primary medium effect, and 4) standard quantities for transfer of HBr from water to each mixed solvent. Results for 4) are discussed in terms of acid-base properties and structure of solvent.

potentiometry; HBr; 2-propanol-water mixtures; thermodynamic quantities

projekt II/1-1975