Thermodynamic study o f ternary [NaCl+Na۲HPO۴ +H۲O] electrolyte s ystem

Recently, there has been an increasing amount of work conc erning the investigation of the thermodynamic properties of mixed aqueous electrolyte solutions because of their im portance in area s such as c hemistry [۱-۲]. The solutions o f sodium o r potassiu m dihydrog en and hydrogen phosphates have been used extensively as stand ard buffer solutions for pH measurements. In the face of their importance, study of the thermodynamic properties on the most a queous mixtures of th ese phosph ate salts es pecially at higher mol alities has not been perform ed [۳]. In the present study, the results relating to the thermodynamic properties for the tern ary mixture of (NaCl + Na۲HP O۴ +H۲O) over total ionic strengths from ۰.۰۱۳۰ to ۴.۰۰۰ mol. kg-۱ for different series of sa lt molal ratios r (r = m NaCl /mNa۲HPO۴=۲.۵, ۵.۰, ۷.۵, ۱۰.۰) a nd pure Na Cl in aqeous system at T= ۲۹۸.۲K are reported.

کلیدواژه ها:

Activ ity coefficient ، EMF ، Pitzer model ، Na۲HPO ۴ ، NaCl