
TY  - JOUR
A1  - Merakis, T 
A1  - Spiccia, L 
T1  - Early Stages of the Hydrolysis of Chromium(III) in Aqueous Solution. V. Measurement of the Equilibrium Between Singly and Doubly Bridged Dimer
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1989
VL  - 42
IS  - 9
SP  - 1579
EP  - 1589
KW  - 
UR  - https://doi.org/10.1071/CH9891579 
N2  - Ion-exchange chromatography has been used to measure the equilibrium between singly bridged (SBD) and doubly bridged (DBD) forms of the hydrolytic dimer of chromium(III), at variable [H+] (0.008-0.97 M) and T (288.2-318.2 K) and constant I (1.0 M). From these measurements, the acid dissociation constant, Kal , for SBD, and the equilibrium constant, K, for interconversion between monodeprotonated SBD and DBD have been determined together with their corresponding thermodynamic constants. The results at 298.2K were as follows: K = 10.1( ±0.6) [&#916;Hº = -10( ±3) kJ mol-1 and &#916;Sº=-15( ±9) J K-1 mol-1]; KKal = 1 .83(±0.04) mol dm-3 [&#916;Sº = 30(±1) kJ mol-1 and &#916;Sº= 104(±4) J K-1 mol-1]; Kal = 0.18( ±0.2) mol dm-3 [&#916;Sº= 43(±4) kJ mol-l and &#916;Sº= 128(±13) J K-1 mol-1]. The high Kalis attributed to the participation of monodeprotonated SBD in hydrogen bonding. As the temperature increases, the overall equilibrium (given by KKal ) is driven towards DBD by a dramatic increase in the acidity ( Kal ) of SBD, an increase which more than offsets a concurrent decrease in K. 
ER  -

