Surface tension, surface excess concentration, enthalpy and entropy of surface formation of aqueous salt solutions

Surface tensions of aqueous solutions of sodium salts of chloride, bromide and nitrate; potassium salts of chloride, bromide and nitrate; lithium chloride and potassium iodide has been determined experimentally at different concentrations and temperatures ranging from 0.10 to 2.00 mol kg−1 and 10–30 °C, respectively. Concentration and temperature dependence of the surface tension of the selected salts has been studied for further estimation of surface excess concentration, enthalpy and entropy of surface formation. The results show that the surface excess concentration decreases linearly with concentration but remains almost constant with the variations of temperature. Similarly the enthalpy of surface formation was observed to decrease with concentration but remained almost constant with the change in temperature. The entropy of surface formation was found to decrease with concentration in most cases.

Concentration dependence of surface excess concentration of KBr solutions at different temperatures.Figure optionsDownload as PowerPoint slideHighlights
► Determination of surface tension and density for 10 different salt solutions.
► Estimation of surface excess concentration, enthalpy, entropy of surface formation.
► Decrease in enthalpy of surface formation with concentration.
► Decrease in entropy of surface formation due to double layer formation.