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Title: Solubility of pyromorphite Pb 5(PO 4) 3Cl at 5–65°C and its experimentally determined thermodynamic parameters

Here, the solubility of synthetic pyromorphite Pb 5(PO 4) 3Cl was determined in a series of dissolution experiments conducted at 5–65 °C and at pH = 2.0. The equilibrium was established within 4 months. The dissolution of pyromorphite was congruent at all the temperatures, and the measured solubility product log K sp,298 for the dissolution reaction: Pb 5(PO 4) 3Cl ⇌ 5Pb 2+ + 3PO 4 3- + Cl - was determined to be –79.6 ± 0.15. The equilibrium ion activity product of pyromorphite increased with temperature, indicating a positive enthalpy of the dissolution reaction in the temperature range from 5 to 65 °C. The temperature dependence of the log K sp was nonlinear: log K sp = A – B/T + D log(T), where A = 478.77 ± 136.62, B = 29,378 ± 6215, and D = –185.81 ± 46.77. This allowed for calculation of ΔG° r = 454.0 ± 1.7 kJ·mol –1, ΔH° r = 101.8 ± 6.0 J·mol –1·K –1, ΔC° p,r = –1545 ± 388.9 J·mol –1·K –1, and ΔS° r = –1181 ± 382 J·mol –1·K –1 of the dissolution reaction. Using these values and the published standard state quantities for constituent ions, the valuesmore » of ΔG° f = –3764.3 ± 3.5 kJ·mol –1, ΔH° f = –4108.4 ± 7.9 J·mol –1·K –1, S° f = 622 ± 382 J·mol –1·K –1, and C° pf = 402 ± 398 J·mol –1·K –1 were calculated for synthetic pyromorphite Pb 5(PO 4) 3Cl.« less
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [3]
  1. AGH Univ. of Science and Technology, Krakow (Poland)
  2. Argonne National Lab. (ANL), Argonne, IL (United States)
  3. Predictive Solutions, Krakow (Poland)
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Thermodynamics
Additional Journal Information:
Journal Volume: 98; Journal Issue: C; Journal ID: ISSN 0021-9614
Publisher:
Elsevier
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
Polish National Science Centre (NCN); AGH University of Science and Technology; USDOE
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; dissolution experiment; lead apatite; pyromorphite; solubility product; thermodynamics
OSTI Identifier:
1339458