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Journal of Structural Chemistry

2014 year, number 4

H 2O-NH 4Cl SYSTEM: THERMODYNAMICS AND STRUCTURE OF SUPERSATURATED (8Г·28 m) SOLUTIONS AT 298.15 K

V. P. Korolev
Krestov Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, Russia
Keywords: термодинамика, водный раствор, хлорид аммония, thermodynamics, aqueous solution, ammonium chloride

Abstract

Thermodynamic characteristics are determined for supersaturated (8÷28 m ) aqueous ammonium chloride solutions at 298.15 K: activity as well as partial molar enthalpy, volume, and excess entropy of water, osmotic coefficients, density, and salt hydration numbers. The relative humidity above the solution decreases from 75.6% (8 m solution) to 44.7% (28 m solution). A directly proportional dependence is found between the enthalpy and entropy characteristics. The negative values of the nonideal portion of the Gibbs energy are due to structural effects (excess entropy). The excess entropy of water has the same value 1.8 J/(mol×K) in supersaturated 12 m NaCl and 28 m NH 4Cl. The ratio 12/28 = 3/7 is also valid for other "isoentropic" molalities of the said salts.