Comprehensive Study of the Hydration and Dehydration Reactions of Carbon Dioxide in Aqueous Solution

Abstract

The reversible interactions of dissolved CO(2) with H(2)O and OH(-) to form H(2)CO(3) and HCO(3)(-) in aqueous solution have been investigated using spectrophotometric stopped-flow measurements. The progress of the reactions was monitored via indicators coupled to the pH changes during the reactions. The study, involving global analysis of the complete data set, spanned the temperature range 6.6-42.8 degrees C and resulted in the evaluation of all rate and equilibrium constants as well as activation parameters for the kinetic data and the reaction enthalpies and entropies for the equilibrium constants.

Chemistry of riming: the retention of organic and inorganic atmospheric trace constituents

“…In the presence of CO 2 (at alkaline pH) the reaction given by Reaction (R3) becomes important and inhibits the reverse Reaction (R2). CO 2 (aq) reacts fast with OH − and forms HCO − 3 (k R3 = 2.3×10 3 s −1 at 6.6 • C; Wang et al, 2010). However, the reverse reaction is very slow (k −R3 = 1.4 × 10 −5 s −1 at 6.6 • C; Wang et al, 2010) so that the opportunity of the OH − ions to recombine with NH + 4 in order to form the volatile aqueous NH 3 (aq) is hindered.…”

“…CO 2 (aq) reacts fast with OH − and forms HCO − 3 (k R3 = 2.3×10 3 s −1 at 6.6 • C; Wang et al, 2010). However, the reverse reaction is very slow (k −R3 = 1.4 × 10 −5 s −1 at 6.6 • C; Wang et al, 2010) so that the opportunity of the OH − ions to recombine with NH + 4 in order to form the volatile aqueous NH 3 (aq) is hindered. By also applying a convective diffusion model including internal circulation of the liquid within the falling drop, it was shown (Hannemann, 1995) that the time to completely deplete a drop of 2.88 mm in radius from NH 3 and to reduce CO 2 back to equilibrium conditions would be 1200 s. This timescale is taken into account in the retention indicator calculation as τ r (Eq.…”

The hydration structure of dissolved carbon dioxide from X-ray absorption spectroscopy

“…The chemical reaction of CO 2 with water to form carbonic acid is clearly the central feature of these carbonate equilibria, and has been addressed by many experiments [5,16,[18][19][20][21][22][23][24][25][26] and calculations [17,[27][28][29][30][31][32][33][34][35][36] with conflicting results. Details of the neutral CO 2 solvation by bulk water prepare the reaction pathway, and are thus a determining factor in this chemistry.…”

The hydration structure of aqueous carbonic acid from X-ray absorption spectroscopy

“…As described in a very recent review [7], carbonic acid has been well studied in both the gas phase [8][9][10] and in cryogenic matrixes [11][12][13][14][15], but there have been very few successful spectroscopic studies of the aqueous acid, and none of its electronic structure [16][17][18]. Carbonic acid is intrinsically unstable upon contact with even a single water molecule, reacting via a proton chain mechanism to rapidly form aqueous bicarbonate, carbonate, and hydrated protons [19][20][21], which comprises the reversible mechanism for dissolution of CO 2 gas.…”