Stability of the magnesium carbonate ion pair from 10 to 90/sup 0/C

Journal Article · Wed Jun 01 04:00:00 EDT 1977 · Am. J. Sci.; (United States)

DOI:https://doi.org/10.2475/ajs.277.6.716· OSTI ID:7293190

Siebert, R M ^[1]; Hostetler, P B

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1. Univ. of Missouri, Columbia

The dissociation constants of the aqueous MgCO/sub 3//sup 0/ ion pair were determined experimentally from 10 to 90/sup 0/C at 15/sup 0/ intervals. Absolute pH measurements in MgCl/sub 2/--KHCO/sub 3/ solutions being titrated with K/sub 2/CO/sub 3/ were used to calculate the results. The experimental pK/sub MgCO/sub 3//sup 0// (-log K/sub dissociation/) at 25/sup 0/C is 2.98 +- 0.03, and the pK values rise smoothly, as a function of temperature, to a value of 3.41 +- 0.067 at 90/sup 0/C. The temperature variation is in excellent agreement with that predicted by electrostatic ion pair theory. The derived values of ..delta..G/sub R//sup 0/, ..delta..H/sub R//sup 0/, and ..delta..S/sub R//sup 0/ of dissociation at 25/sup 0/C are 17050 +- 125 J mol/sup -1/ (4075 +- 30 cal mol/sup -1/, -8439 J mol/sup -1/ (-2017 cal mol/sup -1/), and -85.48 J deg/sup -1/ mol/sup -1/ (-20.43 cal deg/sup -1/ mol/sup -1/), respectively.

• OSTI ID: 7293190
• Journal Information: Am. J. Sci.; (United States), Journal Name: Am. J. Sci.; (United States) Journal Issue: 6 Vol. 277:6; ISSN AJSCA
• Country of Publication: United States
• Language: English

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ACID CARBONATES
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
AQUEOUS SOLUTIONS
CARBON COMPOUNDS
CARBONATES
CATIONS
CHARGED PARTICLES
CHEMICAL REACTION KINETICS
CHLORIDES
CHLORINE COMPOUNDS
DISPERSIONS
HALIDES
HALOGEN COMPOUNDS
IONS
KINETICS
MAGNESIUM CARBONATES
MAGNESIUM CHLORIDES
MAGNESIUM COMPOUNDS
MEDIUM TEMPERATURE
MIXTURES
OXYGEN COMPOUNDS
PH VALUE
POTASSIUM CARBONATES
POTASSIUM COMPOUNDS
REACTION KINETICS
SOLUTIONS
STABILITY
TEMPERATURE DEPENDENCE
TITRATION