HCO2 dissociation

Formic acid (HCO2H) is an organic acid secreted by ants and stinging nettles. Calculate the pH and the concentrations of all species present (HCO2H, HCO2-, H3O+,andOH-)in0.20MHCO2H(Ka = 1.8 X 10 4). Also calculate the percent dissociation. 

The time behavior of the system can be probed by a probe pulse with the wavelength X2 tuned to the transition from Vi(/ ) into the excited state V2(/ ) that dissociates into Na +1. At the fixed wavelength X2 = Inc 10)2 the dissociating system absorbs the probe pulse only at that distance R where V R) — V2 R) = hco2. If X2 is tuned to the sodium resonance line 3 3/7, absorption occurs for R — oo. 

Since the dissociation time is very short compared to the lifetime of the excited sodium atom Na (3/7), the dissociating (Nal) emits nearly exclusively at the atomic resonance fluorescence. The atomic fluorescence intensity /piCNa, Ar), monitored in dependence on the delay time Ar between the pump-and-probe pulse, gives the probability for finding the excited system [Nal] at a certain intemuclear separation R, where V R)— V2 R) = hco2 (Fig. 11.62b). 

It has generally been assumed that most of the reaction mechanisms that occur for WGS are also applicable for RWGS. The two main mechanisms proposed for WGS reactions are (1) surface redox mechanism and (2) dissociative mechanism of water to afford OH and H species, with subsequent formation of formate species (HCO2-M, obtained by an attack of OH groups on M-CO moieties) or metalla carboxyl species (MO2H, which might result from the reaction of M-H moieties with CO2 or, even better, by protonation of metal-bound CO2 see Chaps. 2 and 4) as intermediates [200]. 

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