CgHio p-Xylene

Reaction-equilibrium calculations may be useful for estimation of the compositions of hydrocarbon feedstocks. A particular feedstock, available as a low-pressure gas at 500 K, is identified as "aromatic C8. ft could in principle contain the CgHio isomers o-xylene (OX), nr-xylene (MX), p-xylene (PX), and ethylbenzene (EB). Estimate how nrueh of each species is present, assuming the gas mixture has come to equilibrium at 500 K and low pressure. The following is a set of indepeirdent reactions (why ) ... 

Suppose, for example, that we are trying to identify an unknown liquid of formula CgHio and boiling point 137-139 that we have shown. in other ways to be an alkylbenzene (Sec. 12.22). Looking in Table 12.1 (p. 375), we find that it could be any one of four compounds o-, w-, or p-xylene, or ethylbenzene. As shown below, oxidation of each of these possible hydrocarbons yields a different acid, and these acids can readily be distinguished from each other by their melting points or the melting points of derivatives. 

Molecular formulae are expressed in terms of residues (connected atomic groupings), e.g. CBr4, CgHio for the complex between carbon tetrabromide and p-xylene and CH02, Na+ for sodium formate. 

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