Thermodynamics of calcium-isotope-exchange reactions. 1. Exchange between isotopic calcium carbonates and aqueous calcium ions
This paper reports the authors results for the direct experimental determination of the equilibrium constant for the calcium-isotope-exchange reaction /sup 40/CaCO/sub 3/(s) + /sup 44/CaCl/sub 2/(aq) reversible /sup 44/CaCO/sub 2/(s) + /sup 40/CaCl/sub 2/(aq). The reaction was studied in electrochemical double cells without liquid junction of the type shown in eq 2. The experimental value of the equilibrium constant at 295 +/- 2 K is K = 1.08 +/- 0.02. The experimental value for K is compared with the values of K calculated for various model reactions according to the statistical thermodynamic theory of isotope effects. The isotopic solid carbonates were modeled according to both the Debye and Kieffer theories. No structured models of solvated isotopic aqueous calcium ions yield calculated equilibrium constants in agreement with their experimental results. This conclusion is in agreement with published molecular dynamics calculations which show that the aqueous solvation of Ca/sup 2/=(aq) is essentially unstructured.
- Research Organization:
- Univ. of California, Davis (USA)
- OSTI ID:
- 6333018
- Journal Information:
- J. Phys. Chem.; (United States), Vol. 92:13
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CALCIUM 40
ISOTOPIC EXCHANGE
CALCIUM 44
CALCIUM CARBONATES
CHEMICAL REACTIONS
CALCIUM CHLORIDES
CATIONS
EXPERIMENTAL DATA
THERMODYNAMICS
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CALCIUM HALIDES
CALCIUM ISOTOPES
CARBON COMPOUNDS
CARBONATES
CHARGED PARTICLES
CHLORIDES
CHLORINE COMPOUNDS
DATA
EVEN-EVEN NUCLEI
HALIDES
HALOGEN COMPOUNDS
INFORMATION
INTERMEDIATE MASS NUCLEI
IONS
ISOTOPES
LIGHT NUCLEI
NUCLEI
NUMERICAL DATA
OXYGEN COMPOUNDS
STABLE ISOTOPES
400202* - Isotope Effects
Isotope Exchange
& Isotope Separation