Medium effects and other thermodynamic quantities in 5 wt.% 2-methyl-1-propanol between 5 and 45°C

The standard potentials of the Ag-AgCl electrode in 5 wt.% 2-methyl-1-propanol at five temperatures from 5 to 45°C have been determined by a polynomial curve-fitting technique, using a cell of the type: Pt; H₂ (g, 1 atm) | HCl (m) in 5 wt.% 2-methyl-1-propanol | AgCl, Ag. The values can be fitted in the form of equation obtained by using the least squares method: E^o_m = 0.20350-6.891 x 10^-4(t-25) - 17.563 x 10^-6(t - 25)These values have been used to derive (a) the activity coefficients of HCl, (b) the relative partial molal enthalpy and heat capacity of HCl, (c) the primary medium effect, and (d) the thermodynamic functions (ΔG^o, ΔS^o, and ΔH^o) for the transfer of HCl from water to 5 wt.% 2-methyl-1-propanol. The molality of the acid ranged from 0.005 to 0.09 mol kg^-1. The significance of the data has been discussed in terms of the acid-base properties and the structure of water and of mixed solvents on the transfer process.