CO2 System Hydration and Dehydration Kinetics and the Equilibrium CO2/H2CO3 Ratio in Aqueous NaCl Solution

• Published in: Marine Chemistry
• Main Authors: Soli, Alan L., Byrne, Robert H.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Digital Commons @ University of South Florida 2002
• Subjects: Carbonic acid; Hydration; Dehydration; Carbon dioxide system; Kinetics; Life Sciences
• Online Access: https://digitalcommons.usf.edu/msc_facpub/1736; https://doi.org/10.1016/S0304-4203(02)00010-5

Observations of pH on a millisecond time scale were used to obtain the CO2 hydration rate, the H2CO3 dehydration rate, the ionization constant of H2CO3, and the equilibrium ratio of CO2 and H2CO3 concentrations over a range of temperature (15–32.5 °C). In 0.65 molal NaCl, close to the ionic strength of seawater, the H2CO3 dehydration rate constant (kD) is well represented by the equationlnkD(s−1)=30.15−(8018)T−1,">lnkD(s−1)=30.15−(8018)T−1, and the ionization constant, Ka, for H2CO3 followed the relationshiplogKa=−0.994−(610.5)T−1,">logKa=−0.994−(610.5)T−1, where T is the temperature (Kelvin scale). The equilibrium ratio (KD) of CO2 and H2CO3 concentrations at 25 °C was equal to 848. KD ranged from approximately 840 at 15 °C to 878 at 32.5 °C. Values of KD and kD were used to calculate the CO2 hydration rate constant, kH. Over the temperature range of this work, kH was well represented by the equationlnkH(s−1)=22.66−(7799)T−1.">lnkH(s−1)=22.66−(7799)T−1.