A novel crystalline bis(n-undecylammonium) tetrachlorozincate (C11H23NH3)(2)ZnCl4(s) was synthesized by liquid phase reaction. X-ray single crystal diffraction technique, chemical analysis, and elementary analysis were used to determine crystal structure and chemical composition of the complex. Lattice potential energy was calculated to be U-POT = 873.05 kJ . mol(-1) from crystallographic data. Molar enthalpies of dissolution of the compound at different molalities in the double-distilled water were measured with an isoperibol solution-reaction calorimeter at T = 298.15 K. On the basis of Pitzer's electrolyte solution theory, molar enthalpy of dissolution of (C11H23NH3)(2)ZnCl4(s) at infinite dilution was calculated to be Delta sH(m)(infinity) = (42.67 +/- 0.340) kJ . mol(-1), and sums of Pitzer parameters (4 beta C11H23NH3,Cl-(0)L + 2 beta((0)L)(Zn,Cl) + theta C11H23NH3,Zn-L) and 2 beta C11H23NH3,Cl(1)L + beta((1)L)(Zn,Cl)) were obtained. In addition, the molar enthalpy of hydration of the cation [C11H23NH3]+ in the complex (C11H23NH3)(2)ZnCl4(s) was calculated to be Delta H+ = -(25.52 +/- 0.878) kJ . mol(-1) by designing a thermochemical cycle based on lattice potential energy and molar enthalpy of dissolution of the title complex at infinite dilution. (C) 2012 Elsevier Ltd. All rights reserved.