Thermochemistry of inorganic sulfur compounds V. Peroxymonosulfate revisited: standard molar enthalpies of formation of KHSO5·H2O(cr), KHSO5(cr), and HSO5−(aq)
1985; Elsevier BV; Volume: 17; Issue: 5 Linguagem: Inglês
10.1016/0021-9614(85)90146-6
ISSN1096-3626
AutoresP.A.G. O’Hare, L. J. Basile, Evan H. Appelman,
Tópico(s)Chemical Thermodynamics and Molecular Structure
ResumoThe enthalpy of reaction of pure KHSO5·H2O with HI(aq) has been determined calorimetrically. This result has been combined with auxiliary enthalpy-of-solution measurements to yield the standard molar enthalpy of formation: ΔfHmo(KHSO5·H2O, cr, 298.15 K) = −(1359.88±0.57) kJ·mol−1. The standard molar enthalpies of solution in water of KHSO5·H2O and KHSO5 have also been measured: ΔslnHmo(KHSO5·H2O, cr, 298.15 K) = (46.24±0.34) kJ·mol−1, ΔslnHmo(KHSO5, cr, 298.15 K) = (33.68±0.24) kJ·mol−1. From these results, ΔfHmo(HSO5−, aq) with standard molality mo = 1 mol·kg−1, has been calculated to be −(775.64±0.68) kJ·mol−1. The standard potential for the aqueous half-reaction: HSO5− + 2H+ + 2e− = HSO4− + H2O, is estimated to be (1.85±0.03) V. Also reported are ΔfHmo(KHSO5, cr, 298.15 K) = −(1061.49±0.71) kJ·mol−1; the molar enthalpy of dehydration at 298.15 K for the reaction: KHSO5·H2O(cr) = KHSO5(cr) + H2O(l), ΔfHmo = (12.56±0.42) kJ·mol−1; and the equilibrium H2O(g) vapor pressure at 298.15 K for the dehydration reaction: KHSO5·H2O(cr) = KHSO5(cr) + H2O(g), ppo = (7.1±1.0) × 10−3. Taking po = 101325 Pa, the vapor pressure is (720±100) Pa.
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