Carbon dioxide acid-base chemistry

Chemists use whatever tools they can find in their laboratories to take full advantage of the properties of acids and bases. One tool they use is Kipp s apparatus, a piece of laboratory equipment that relies on acid-base chemistry to do its job. Named for its inventor, Dutch pharmacist Petrus Johannes Kipp (1808-1864), Kipp s apparatus (or gas generator) is especially useful for creating gases, such as carbon dioxide, hydrogen, or hydrogen sulfide, that the chemists can then use in other chemical reactions. 

Figure 5.1 Made with three connected glass bowls, Kipp s apparatus relies on acid-base chemistry in order to produce gasses—such as carbon dioxide, hydrogen, or hydrogen sulfide—for chemists to use in other chemical reactions.

Carbonate equilibria in an open system. What is the pH of water in equilibrium with atmospheric C02 gas To answer such a question involves a knowledge of acid-base chemistry, the use of Henry s Law constant for the solubility of carbon dioxide and the use of the ENE to calculate the proton concentration of the equilibrium solution. The details of the equilibrium constants used are detailed below. 

The fallacy is that we neglected the contribution of the reaction H2O H + OH" to the concentration of OH". Pure water creates 10" M OH", which is more OH" than the KOH that we added. The pH of water plus added KOH cannot fall below 7. The pH of 4.2 X 10 M KOH is very close to 7. Similarly, the pH of 10" M HNO3 is very close to 7, not 10. Figure 8-3 shows how pH depends on concentration for a strong acid and a strong base. In a very dilute solution exposed to air, the acid-base chemistry of dissolved carbon dioxide (CO2 + H2O HCO 3 + H ) would overwhelm the effect of the added acid or base. 

Many important biochemical reactions involve Lewis acid Lewis base chemistry Carbon dioxide is rapidly converted to hydrogen carbonate ion m the presence of the enzyme carbonic anhydrase... 

Oxidative Carbonylation of Ethylene—Elimination of Alcohol from p-Alkoxypropionates. Spectacular progress in the 1970s led to the rapid development of organotransition-metal chemistry, particularly to catalyze olefin reactions (93,94). A number of patents have been issued (28,95—97) for the oxidative carbonylation of ethylene to provide acryUc acid and esters. The procedure is based on the palladium catalyzed carbonylation of ethylene in the Hquid phase at temperatures of 50—200°C. Esters are formed when alcohols are included. Anhydrous conditions are desirable to minimize the formation of by-products including acetaldehyde and carbon dioxide (see Acetaldehyde). 

The electrolytes Na", and Cl are second only to glucose in being the most frequently run hospital tests. Many clinical chemistry analyzers now contain an ISE module for electrolyte analysis. Most commonly the module will consist of a Na -glass electrode, a valinomycin/PVC electrode, a Ag/AgCl pellet or a quaternary ammonium ion/PVC electrode and a reference electrode. A selective electrode for the bicarbonate ion continues to elude workers in the field. An indirect measurement of HCOf must be made. The sample is usually reacted with acid to evolve carbon dioxide gas which is measured with a traditional Severinghaus type CO2 electrode. Alternatively, the sample is treated with base to convert HCO to CO3 and a carbonate ion-selective electrode is used In this manner, the complete primary electrolyte profile is obtained electrochemically. 

Perhaps no two classes of compounds are more important in chemistry than acids and bases. All acids have several properties in common They have a sour taste, and they all react with most metals to form hydrogen gas (Hj) and with baking soda to form carbon dioxide (CO2). All acids turn blue litmus paper red, and their solutions conduct electricity because acids form ions when dissolved in water. t 11 bases also share several common properties They have a bitter taste, their solutions feel slippery like soapy water, and they turn red litmus paper blue (the opposite of acids). Solutions of bases also conduct electricity because they too form ions in water. Acids are similar because they produce hydrogen ion, (aq), in water. Bases, on the other hand, all form hydroxide ion, 0 [ (aq), in water. These ions are responsible for the properties of acids and bases. 

Almost all of the reactions that the practicing inotganic chemist observes in the laboratory take place in solution. Although water is the best-known solvent, it is not the only one of importance to the chemist. The organic chemist often uses nonpolar solvents sud) as carbon tetrachloride and benzene to dissolve nonpolar compounds. These are also of interest to Ihe inoiganic chemist and, in addition, polar solvents such as liquid ammonia, sulfuric acid, glacial acetic acid, sulfur dioxide, and various nonmctal halides have been studied extensively. The study of solution chemistry is intimately connected with acid-base theory, and the separation of this material into a separate chapter is merely a matter of convenience. For example, nonaqueous solvents are often interpreted in terms of the solvent system concept, the formation of solvates involve acid-base interactions, and even redox reactions may be included within the (Jsanovich definition of acid-base reactions. 

A broader definition than that confined to solutions is demanded in some fields of chemistry (e.g., in high temperature reactions of acids, bases, and salts). In the foimation of metallulgical slags, at furnace tempeiatuies, calcium oxide is used as base and silicon oxide and aluminum oxide as acids calcium aluminosilicate is produced as a fused salt. Sodium carbonate and silicon oxide when fused react to form the salt sodium silicate with the evolution of carbon dioxide. In this sense ... 

Prior to a discussion of C02 insertion reactions into M-H and M-C bonds it is useful to review some of the known coordination chemistry of carbon dioxide, since activation of COz by metal centers is assumed to be of significance in most of these processes. Carbon dioxide can interact with metal centers by three functionalities. These include the Lewis acid site at carbon (1), the Lewis base sites of the terminal oxygen atoms (2), and the t]2 C=0 bond (3). It is possible as well that a combination... 

The uncatalysed Belousov-Zhabotinsky (B-Z) reaction between malonic acid and acid bromate proceeds by two parallel mechanisms. In one reaction channel the first molecular products are glyoxalic acid and carbon dioxide, whereas in the other channel mesoxalic acid is the first molecular intermediate. The initial reaction for both pathways, for which mechanisms have been suggested, showed first-order dependence on malonic acid and bromate ion.166 The dependence of the maximal rate of the oxidation of hemin with acid bromate has the form v = [hemin]0-8 [Br03 ] [H+]12. Bromate radical, Br02, rather than elemental bromine, is said to play the crucial role. A mechanism has been suggested taking into account the bromate chemistry in B-Z reactions and appropriate steps for hemin. Based on the proposed mechanism, model calculations have been carried out. The results of computation agree with the main experimental features of the reaction.167... 

The chemistry of the carbonic acid system in seawater has been one of the more intensely studied areas of carbonate geochemistry. This is because a very precise and detailed knowledge of this system is necessary to understand carbon dioxide cycling and the deposition of carbonate sediments in the marine environment. A major concept applicable to problems dealing with the behavior of carbonic acid and carbonate minerals in seawater is the idea of a constant ionic medium. This concept is based on the observation that the salt in seawater has almost constant composition, i.e., the ratios of the major ions are the same from place to place in the ocean (Marcet s principle). Possible exceptions can include seawater in evaporative lagoons, pores of marine sediments, and near river mouths. Consequently, the major ion composition of seawater can generally be determined from its salinity. It has been possible, therefore, to develop equations in which the influence of seawater composition on carbonate equilibria is described simply in terms of salinity. 

As pervasive as redox reactions are, however, they are certainly not all there is to chemistry. Another very common and important type of reaction is found in the acid-base reactions that occur in the air, on skin, in stomachs, in sewers, and even in swimming pools and fish tanks. The fish-tank indicator that we used to detect carbon dioxide is an acid-base indicator. It worked to detect carbon dioxide because carbon dioxide dissolved in water turns water slightly acidic. Intrigued Read on. 

Scale is a rock-hard crust that can form in pipes and pots that are used with hard water. Before the general availability of household water softeners, scale was a much more common experience. Insoluble scale forms from calcium ions when carbonate ion is present. This fact highlights, once more, the versatility of carbonates. We have seen carbon dioxide form carbonates and hence carbonic acid in water we have used sodium bicarbonate (baking soda) as a base and finally we have pointed out that carbonates can make fairly insoluble solids. These many talents of the carbonate ion make baking soda good for more than cooking. Baking soda makes an excellent deodorizer because it can react with both acidic and basic smelly compounds and can form nonvolatile, and hence non-smelly, compounds with many more. A lot of chemistry in a little box ... 

Many mechanisms in organic chemistry start with an acid/base reaction. This may be just a simple Bronsted-Lowry protonation of a hydroxyl group, which results in the activation of a C-OH bond or it may be a Lewis acid/base reaction as, for example, when aluminium trichloride complexes with a halogenoalkane in the first step of the Friedel-Crafts reaction. In each case, the initial intermediate usually reacts further and leads to the desired product. In inorganic chemistry, the acid/base reaction may be all that is of interest, e.g. the treatment of a carbonate with an acid to liberate carbon dioxide. However, it is unusual in organic chemistry for the acid/base reaction to be an end in itself. It is for this reason that acid/base characteristics are normally considered as a property of the molecule, similar to the nucleophilic and electrophilic properties to which they are closely related, rather than as a fundamental reaction type as is the case in inorganic chemistry. 

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