Oxides and oxoacids of carbon

Carbon monoxide is a colourless gas, formed when C bums in a restricted supply of O2. Small-scale preparations involve the dehydration of methanoic acid (eq. 14.61). CO is manufactured by reduction of CO2 using coke heated above 1070 K or by the water-gas shift reaction (see Section 10.4). Industrially, CO is very important and we consider some relevant catalytic processes in Chapter 25. The thermodynamics of the oxidation of carbon is of immense importance in metallurgy as discussed in Section 8.8. cone H2SO4 

Selected physical properties of CO and CO2 are given in Table 14.4. Bonding models are described in Sections 2.7 and 5.7. The bond in CO is the strongest known in a stable molecule and confirms the efficiency of (p-p)n-bonding between the 2p orbitals of C and O. However, 

Carbon dioxide normally constitutes paO.04% by volume of the according to the carbon cycle Earth s atmosphere, from which it is removed and returned 

The second major greenhouse gas is CH4 which is produced by the anaerobic decomposition of organic material. The old name of marsh gas came about because bubbles of CH4 escape from marshes. Flooded areas such as rice paddy fields produce large amounts of CH4, and ruminants (e.g. cows, sheep and goats) also expel sizeable quantities of CH4. Although the latter is a natural process, recent increases in the numbers of domestic animals around the world are naturally leading to increased release of CH4 into the atmosphere. 

The 1997 Kyoto Protocol is an international agreement that commits the industriahzed countries that signed it to reducing their levels of emissions of the greenhouse gases CO2, CH4, N2O, SFg, hydrofluorocarbons and perfluorocarbons 

9 Oxides, oxoacids and hydroxides Oxides and oxoacids of carbon 

Carbon monoxide is a colourless gas, formed when C burns in a restricted supply of O2. Small-scale preparations involve the dehydration of methanoic acid (equation 14.61). CO is manufactured by reduction of CO2 using 

In an excess of O2, C burns to give CO2. Under normal temperatures and pressures, CO2 exists as linear molecules with C=0 double bonds. Solid phases containing CO2 molecules can be produced at low temperatures and high pressures. The most commonly encountered example is dry ice which is produced by first liquefying CO2 at a pressure of 6 MPa, and then cooling the liquid CO2 (still under 

Carbon dioxide is the world s major environmental source of acid and its low solubility in water is of immense biochemical and geochemical significance. In an aqueous solution of carbon dioxide, most of the solute is present as molecular CO2 rather than as H2CO3, as can be seen from the value of X 1.7 X 10 for the equihbrium  

Unlike the later elements in group 14, carbon forms stable, volatile monomeric oxides CO and CO2. A comment on 

Carbon monoxide is almost insoluble in water under normal conditions and does not react with aqueous NaOH, but at high pressures and temperatures, HCO2H and Na[HC02] 

The thermodynamics of the oxidation of carbon is of immense importance in metallurgy as we have already discussed in Section 7.8. 

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Structure and bonding in oxides and oxoacids of carbon, sulfur, nitrogen, phosphorus, and chlorine... 

This oxoacidity is described by p02 = - log a(02 ), where a(02 ) is the oxide ion activity [6]. Not surprisingly, the anodic and cathodic potential limits of carbonate melts are very dependent upon the oxoacidity. Anodic decomposition of the melt is assumed to arise from the oxidation of oxide provided by the thermal decomposition of CO ... 

When a nonmetal oxide reacts with water, it forms an oxoacid with the same oxidation number as the nonmetal. Give the name and formula of the oxide used to prepare each of these oxoacids (a) hypochlorous acid (b) chlorous acid (c) chloric acid (d) perchloric acid (e) sulfuric acid (f) sulfurous acid (g) nitric acid (h) nitrous acid (i) carbonic acid (j) phosphoric acid. 

Hydroxides MOH are important compounds for all the alkali metals. They can easily formed by reaction of oxides with water (or atmosphere moisture). They are soluble in water and give strong base. Compounds of oxoacids are commonly encountered, such as carbonate, nitrate, sulphate, etc. as these anions are fairly large, lithium compounds tend to be the most soluble in the series. Many of these compounds crystallise in a variety of hydrated forms (e.g. Na2C03. H2 O with n = 1, 7 or 10). 

In the literature, there are reports of work concerned with the measurement of oxoacidic properties of ionic melts by gravimetric measurements of the solubility of acidic gases in these media [76, 77], The solubility of sulfur(VI) oxide in molten sodium phosphates was determined by the gravimetric method [76], A correlation was obtained between the melt basicities and the solubility of gaseous acid S03 in them. Iwamoto reported the estimation of the basic properties of molten salt by measurements of acidic gas solubilities (carbon dioxide and water) in them [77], However, similar methods cannot be used widely, owing to two factors. The first of these consists in the fact that the solubility of any gas in a liquid phase obeys Henry s law. Let us consider the following system of reactions ... 

Therefore, the addition of organic salts leads to their decomposition into carbonate ions plus the formation of uncontrolled concentrations of nitrite ions owing to the melt reduction. No direct correlation is observed between the weight of such a base and the concentration of oxide ion created, owing to the base dissociation in the melt. This fact makes most of the studied bases unavailable for investigations of oxoacidity in molten salts. 

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