ISSN:
1572-8927
Keywords:
Enthalpy
;
dilution
;
ion pairs
;
lithium, sodium, and potassium chlorides and sulfates
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The enthalpies of dilution of lithium, sodium, potassium, and magnesium chloride and sulfate solutions in the range 0.1 to 1.0 m have been measured at 30°C with a microcalorimeter. The relative apparent enthalpies φL of these solutions have been determined with the aid of an extended form of the Debye-Hückel limiting law $$\phi _L = S_H I^{1/2} [1/(1 + I^{1/2} ) - (\sigma /3)] + {\rm B}{\rm I} + CI^{3/2} $$ whereS H is the limiting-law slope, σ = 3/I3/2 × [(1+I1/2 − 1/(1+I1/2 − 2 ln (2+I1/2)], andB andC are empirical constants. This equation fits the experimental results to within a standard deviation of 2 cal-mole−1 for all the salts. The measured φL for the MgSO4 solutions were compared to those calculated using the additivity principle, φL(MgCl2) + φL(Na2SO4) − 2φL(NaCl), and the extended Debye-Hückel equation. The results of this comparison have been used to calculate the ΔH A o for the formation of MgSO 4 0 . A value of ΔH A o = 1.15 to 1.36 was obtained, depending upon the φL estimates for the free ions Mg2+ and SO 4 2− . The results are briefly discussed and compared to the results obtained by other workers.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00649155
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