- 作者: 潘貫; 辛淑琴; 李明蓉
- 作者服務機構: Chemistry Research Center, National Taiwan University
- 中文摘要: The solubility-product constant f LaF3(s) obtained by potentiometric titration of sodium fluoride with lanthanum perchlorate in sodium perchlorate solution of various ionic strengths. The limiting value of pKs.p. were found to be 17.65 and 17.95 at 20° and 25°, respectively. Thermodynamic calculation from these values gives ⊿G°=-102.46 kJ mol¯1, ⊿H°=100.40 kJ mol¯1 and ⊿S°=680.40JK¯1 mol¯4 for the reaction, La+3(aq)+3F¯(aq)=LaF3(s), and ⊿G..°=-1613.8° kJ mol¯1, ⊿H..°=-1594.0 kJ mol¯1, and S°=433.1JK¯1 mol¯1 for the formation of LaFs(s) at 25℃. The mean activity coefficients and solu-bilities of LaFs(s) in NaClO4 solution at various ionic strengths at 25℃ were evaluated.
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