Reaction methods gaseous product collection

Ti/Si binary oxides having different Ti contents were prepared by the sol-gel method from mixtures of tetraethylorthosilicate and titaniumisopropoxide. Ti/Si gels were obtained by keeping the mixture at room temperature for several days, washed with sufficient amounts of boiled water and then calcined in dry air at 725 K for 5 h. The Ti/Si binary oxides were crushed and sieved to 0.25-mm-size particles. Prior to spectroscopic measurements and photocatalytic reactions, the catalysts were treated with O2 at 725 K for 2 h and then evacuated for 2 h at 475 K. The photocatalytic reduction of CO2 with H2O was carried out with the catalysts (150 mg) in a quartz cell connected to a conventional vacuum system. UV irradiation of the catalysts in the presence of CO2 (24 pmol) and gaseous H2O (120 pmol) was carried out using a high-pressure Hg lamp (X, > 280 nm) at 328 K. The reaction products collected in the gas phase were analyzed by gas chromatography. 

One of the methods of determining the percent composition by mass of a mixture is to measure quantitatively the amount of product formed by reaction of one of the components under conditions where the other component is inert and remains unreacted. If one of the products is a gas, that gas can be collected, its volume can be determined under measured conditions of pressure and temperature, and the number of moles of gaseous product can be calculated using a rearranged form of the Ideal Gas Law. The moles of product can be related back to the moles and mass of reactant from which the product was formed. By knowing the mass of one component which reacted, the mass of the other component can then be determined by difference from the total mass of unknown mixture used. Finally, percent composition by mass can be calculated. 

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