The article ??Enthalpies and Entropies of Transfer of Electrolytes and Ions from Water to Mixed Aqueous Organic Solvents?? (G. Hefter, Y. Marcus, andW.Waghorne, Chemical Reviews, 2002:2773??2836) presents measurements of entropy and enthalpy changes for many salts under a variety of conditions. The following table presents the results for enthalpy of transfer (in kJ/mol) from water to water + methanol of NaCl (table salt) for several concentrations of methanol. Four independent measurements were made at each concentration.

a. Is it plausible that the enthalpy is the same at all concentrations? Explain.

b. Which pairs of concentrations, if any, can you conclude to have differing enthalpies?

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Concentration (%) Enthalpy 5 1.62 1.60 1.62 1.66 10 2.69 2.66 2.72 2.73 20 3.56 3.45 3.65 3.52 30 3.35 3.18 3.40 3.06