共查询到20条相似文献,搜索用时 31 毫秒
1.
A high pressure UV-visible spectrophotometer was used to determine the dissociation constant of boric acid using an indicator technique. The measurements were made at 25°C and at ionic strengths of 0.1 and 1.0m over a pressure range of 1 to 2000 atm. Extrapolation to I=0 gave a thermodynamic dissociation constant of 5.16×10–10 at 1 atm. The pressure dependence yielded a partial molal volume change of –28.9 and –31.8 cm3-mol–1 and a compressibility change of –3.1 and –4.8×10–3 cm3-mol–1-atm–1 for the dissociation at I=0.1 and 1.0m, respectively. The association constant for the formation of the sodium borate ion pair was determined by comparing the acid constants in tetramethylammonium chloride to those in sodium chloride solutions. Extrapolation to I=0 yielded a KA for [NaB(OH)4] of 0.64 at 1 atm. The pressure dependence of KA gave
and
for the formation of the ion pair. 相似文献
2.
A flow heat capcity calorimeter and a flow vibrating tube densimeter have been used to measure the apparent molal heat capacities and volumes of benzene and 25 polar compounds in methanol at 25°C. These quantities have been extrapolated to infinite dilution to obtain the standard partial molal heat capacities and volumes. The
and
data have been used in conjunction with an additivity scheme previously determined for alkanes. Group contributions were evaluatd for –OH, –NH2, –COOH, –C6H5, C=O, –COO–, –CONH–, –O–, –S–, and –S2–. The concentration dependences of cp and v of nonelectrolytes in methanol are qualitatively similar but much smaller than in water. 相似文献
3.
The solubility of Cd(OH)2(c) was studied in 0.01M NaClO4 solutions, from both the over- and the undersaturation directions, with OH– ion concentration ranging from 10–6 to 1.0 mol-L–1, and the equilibration period ranging from 2 to 28 days. Equilibrium Cd concentrations were reached in less than 2 days. The Cd(OH)2(c) solubility showed an amphoteric behavior. In the entire range of OH–/H+ investigated, the only dominant aqueous Cd(II) species required to explain the solubility of Cd(OH)2(c) are Cd2+, Cd(OH)
2
0
, and Cd(OH)
4
2–
. The logarithms of the thermodynamic equilibrium constants of the Cd(OH)2(c) solubility reactions involving these species, that is, the reactions
相似文献
4.
Virender K. Sharma Fabien Casteran Frank J. Millero Concetta De Stefano 《Journal of solution chemistry》2002,31(10):783-792
The sulfur-containing biomolecule, cysteine has a role in physiological and natural environment because of its strong interactions with metals. To understand these interactions of metals with cysteine, one needs reliable dissociation constants for the protonated cysteine species [
CH(CH2SH)COOH; H3B+]. The values of dissociated constants, p
, for protonated cysteine species (H3B+ H+ + H2B, K
1; H2B H+ + HB–,K
2; HB– H+ + B2–,K
3) were determined from potentiometric measurements in NaCl solutions as a function of ionic strength, 0.5–6.0 mol-(kgH2O)–1 and between 5, and 45°C. The equations
5.
A platinum-lined flowing autocláve facility was used to investigate the solubility behavior of magnetite (Fe3O4) in alkaline sodium phosphate and ammonium hydroxide solutions between 21 and 288°C. Measured iron solubilities were interpreted via a Fe(II)/Fe(III) ion hydroxo-, phosphato-, and ammino-complexing model and thermodynamic functions for these equilibria were obtained from a least-squares analysis of the data. A total of 14 iron ion species were fitted. Complexing equilibria are reported for 8 new species: Fe(OH)(HPO4)–, Fe(OH)2(HPO4)2–, Fe(OH)3(HPO4)2–, Fe(OH)(NH3)+, Fe(OH)2(PO4)3–, Fe(OH)4(HPO4)3–, Fe(OH)2(H2PO4)–, and Fe(OH)3(H2PO4)3–. At elevated temperatures, hydrolysis and phosphato complexing tended to stabilize Fe(III) relative to Fe(II), as evidenced by free energy changes fitted to the oxidation reactions.
|
设为首页 | 免责声明 | 关于勤云 | 加入收藏 |
Copyright©北京勤云科技发展有限公司 京ICP备09084417号 |