Practice Problems: acid-metal reactions

In order to avoid the autoxidation problem it has become a common practice in the edible oil industry to construct reaction vessels of stainless steel. Citric acid is often added as a metal sequestrant to effectively inactivate trace metal ions. 

Surface Area, Porosity, and Permeability. Some very interesting and important phenomena involve small particles and their surfaces. For example, SO2 produced from mining and smelting operations that extract metals such as Cu and Ph from heavy metal sulfide ores can be oxidized to SO3 in the atmosphere, thus contrihutingto acid rain problems. The reaction rate depends not only on the concentration of the SO2 bnt also on the siuTace area of any catalyst available, such as airborne dnst particles. The efficiency of a catalyst depends on its specific surface area, defined as the ratio of siuTace area to mass (17). The specific snrface area depends on both the size and shape, and is distinctively high for colloidalsized species. This is important in the catalytic processes nsed in many indnstries for which the rates of reactions occurring at the catalyst siuTace depend not only on the concentrations of the feed stream reactants bnt also on the sinface area of catalyst available. Since practical catalysts freqnently are snpported catalysts, some of the sinface area is more important than the rest. Since the supporting phase is usnally porous the size and shapes of the pores may influence the reaction rates as well. The final rate expressions for a catalytic process may contain all of these factors sinface area, porosity, and permeability. 

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