Carbon acids, dissociation

The hydrogen ion flux that is provided by carbonic acid dissociation also can attack calcite (CaCO ) ... 

Let us write the electroneutrality condition, as well as the equations for water and carbonic acid dissociation and finally the saturation condition as... 

Carbonic acid dissociates to produce bicarbonate and hydrogen ions... 

The reactions and the corresponding equilibrium constants for the carbonic acid dissociation are as follows ... 

The Solubility of Carbon Dioxide in Brines. Information required to describe the carbonate system in a brine includes the solubility of carbon dioxide, the extent of carbonic acid formation, and the distribution of the anionic carbonic acid dissociation products HCO3 and C0 . ... 

Goyet C. and Poisson A. (1989) New determination of carbonic acid dissociation constants in seawater as a function of temperature and salinity. Deep-Sea Res. 36, 1635-1654. 

Photochemical carbon acid dissociation has been studied in considerable detail by Wan and his coworkers. The current work has examined the photochemical behaviour of the dibenzocycloheptene derivatives (149). The influence of substituents on the process was studied. A review has highlighted the photochemical methods for the formation of carbanions. Within the general framework of photodeprotonation of benzylic systems Wan and his coworkers have also reported the results of a study into the photochemical deprotonation of the thioxanthenium salts (150)-(153). The reactions are carried out by irradiation at 254 nm in dry acetonitrile under an argon purge. Prolonged irradiation of compound (150), for example, results in the production of (154) in 60% yield. The authors reason that this product is formed via the intermediacy of the... 

Figure 7.20 Carbon dioxide and pH. Carbon dioxide in the tissues diffuses into red blood cells, Inside a red blood cell, carbon dioxide reacts with water to form carbonic acid, in a reaction catalyzed by the enzyme carbonic anhydrase. Carbonic acid dissociates to form HCOj and H , resulting in a drop in pH inside the red cell.

Carbon dioxide reacts with water to form carbonic acid, H CX) i. ITiis reaction is accelerated by carbonic anhydnise, an enzyme abundant in red blood cells that will be considered extensively in Chapter 9. Carbonic acid is a strong acid with a pK, of 3.5. Thus, once formed, carbonic acid dissociates to form bicarbonate ion, HCO.Ct cind H, resulting in a drop in pH. This drop in pH stabilizes the T state by the mechanism discussed previously. 

Because bicarbonate is a small ion, it is freely filtered at the glomerulus. The bicarbonate load delivered to the nephron is approximately 4,500 mEq/day. To maintain acid-base balance, this entire filtered load must be reabsorbed. Bicarbonate reabsorption occurs primarily in the proximal tubule (Fig. 51-1). In the mbular lumen, filtered bicarbonate combines with hydrogen ion secreted by the apical Na+-H+-exchanger to form carbonic acid. The carbonic acid is rapidly broken down to CO2 and water by carbonic anhydrase located on the luminal surface of the brush border membrane. The CO2 then diffuses into the proximal tubular cell, where it reforms carbonic acid in the presence of intracellular carbonic anhydrase. The carbonic acid dissociates to form hydrogen ion, that can again be secreted into the tubular lumen, and bicarbonate that exits the cell across the basolateral membrane and enters the peritubular capillary. 

The carbonic acid dissociates, releasing hydrogen ions, which are buffered by nonbicarbonate buffers (i.e., proteins, phosphate, and hemoglobin) and bicarbonate. Thus on the basis of physicochemical factors, increases in PaC02 raise the serum bicarbonate concentration. In general, in acute respiratory acidosis, the bicarbonate concentration increases by 1 mEq/L above 24 for each 10-mm Hg increase in PaC02 above 40 (see Table 51 ). 

If we reconsider K —Na exchange on smectite, nearly ideal two-ion exchange behavior is seen when the process is conducted in 0,01 MNaCl that is, the selectivity coefficient Ks is fairly constant. On the other hand, if the electrolyte concentration is very low, Na cations, and to a lesser extent cations, are exchanged from the clay by protons (more precisely, HjP ions) generated from carbonic acid dissociation. As a result, the apparent value of Ks, if based on the incorrect assumption that only... 

But [H ] is subject to control by carbonic acid dissociation according to equation 3.63. In addition, the dissociation of HCO7 to form COi and release a proton can also influence the equilibrium, but this reaction can be neglected as long as the equilibrium pH does not rise to very alkaline values. The rule of electroneutrality (charge conservation) requires that the HCOj anions in solution be balanced by Na and H. That is ... 

Consider now the simplest case pure water in equilibrium with CO2 in the soil air. In this instance, [H ] = [HCOf], because the only significant source of acidity in the soil water is carbonic acid dissociation. Equation 5.57 then simplifies to... 

An interesting consequence of the presence of soil solids is that, as higher levels of CO2 in the soil generate more and HCOs" from carbonic acid dissociation,... 

In clean natural water the pH can be calculated from the content of free CO2 and hydrogen carbonates using the expression for the first dissociation constant of carbonic acid. Dissociation to the 2nd degree can be neglected as its effect becomes significant only as pH > 8.3. Due to the inaccurate determination of free CO2 the calculation provides only rough results. On the contrary, from a known value of pH and the content of HCO3 the content of free CO2 can be calculated. 

Chapter 3 in [72DER] includes a solubility study of Zr hydroxide in the presence of varying concentrations of carbonate, conducted at a constant ionic strength of 1 M in NH4NO3. The determinations of the hydroxide solubility product in the absence of carbonate and of the carbonic acid dissociation constants in the same medium, needed for the evaluation of the Zr-C03 data, are also reported in the same chapter. 

Because of the incorrectness of the hydrolysis model used in [72DER], we were forced to re-evaluate these solubility data in terms of the hydrolysis model defined and accepted in this review. In contrast, the (precise) determination of the conditional carbonic acid dissociation constants in 1 M NH4NO3 could be taken without modification and were applied in our re-evaluation. The following constants were determined by [72DER] ... 

In Fig. 6.86 the concentrations of various carbonate ions in solution, as a function of NaOH concentration, are shown. The ions formed as a result of carbonic acid dissociation will relatively quickly react with the calcirrm iorts and calcium carbonate will precipitate from the solution. 

Carbonic acid dissociates to give hydrogen ions and bicarbonate ions. 

The carbonic acid dissociates into ions in two steps (Reactions 2 and 3). 

Thanks are due to Dr G. L. Pickard, Director of the Institute of Oceanography at the University of British Columbia, for permission to include bis tables for the conversion of 20 C chlorosity to salinity. The tables given for calculating the carbonate balance of sea water largely follow the Buch presentation as given by H. W. Harvey in his book The Chemistry and Fertility of Sea Waters (Cambridge University Press, 1957). Thqr have been extended and some have been changed so as to incorporate a more recent estimate of the second carbonic acid dissociation constant by J. Lyman. 

These reactions describe the dissolution of atmospheric carbon dioxide (CO2) in water (reaction 1) and the subsequent reaction forming carbonic acid (2). Once in solution, carbonic acid dissociates forming bicarbonate (HCO3-) and a hydrogen ion (H+ reaction 3). Subsequently, this bicarbonate ion may dissociate to form a carbonate ion and a further hydrogen ion (4). Concurrently, calcium hydroxide (Ca(OH)2) dissolves in water forming calcium and hydroxyl ions (OH- 5). 

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