Abstract:
The partial molar enthalpies of tetra-n-pentylammonium bromide in aqueous urea (up to 7 M urea)
and in aqueous sodium chloride (up to 5 M NaCl) solutions have been determined calorimetrically
at 25 and 35°C. These data have been used to derive the enthalpies of transfer (at 25 and 35CC)
and the heat capacities of transfer (at 30°C) of the salt from water to aqueous urea and aqueous
sodium chloride solutions. The results show that the heat capacities of transfer in aqueous urea
and aqueous sodium chloride solutions have opposite signs. It has been deduced that the structure
breaking effect of urea in the presence of hydrophobic solutes or ions containing hydrophobic parts
is different from that of sodium chloride.
