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Steady-State Approximation, Reaction Mechanism and Rate Law of Chain Reactions
Published in Eli Usheunepa Yunana, Calculations in Chemical Kinetics for Undergraduates, 2022
Elementary reactions are characterized by the following: They are either unimolecular (involves a single reactant species) or bimolecular (involves two reactant molecules), but termolecular (involves three reactant molecules colliding simultaneously) are very rare.The order of an elementary reaction corresponds with the stoichiometric coefficients in the balanced equation for that step, although this is not always true for the overall rate law and overall balanced equation in an experiment.The overall rate law of a reaction depends on a single elementary step which is usually the slowest step in the reaction mechanism.They can also be reversible reactions having both forward and reverse processes at equilibrium.
Catalysis
Published in Aidé Sáenz-Galindo, Adali Oliva Castañeda-Facio, Raúl Rodríguez-Herrera, Green Chemistry and Applications, 2020
Fabiola N. de la Cruz, José Domingo Rivera-Ramírez, Julio López, Miguel A. Vázquez
Generally, the use of catalysts alter the reaction mechanism to reduce the activation energy and make new energy barriers (relative to the uncatalyzed reaction), making it easier for the reactants to overcome this new energy barrier and obtain the products.
Water Chemistry
Published in Louis Theodore, R. Ryan Dupont, Water Resource Management Issues, 2019
Louis Theodore, R. Ryan Dupont
Increasing the temperature of a system imparts more kinetic energy to molecules, thereby serving to increase rates of chemical reactions. The detailed explanation of how a reaction proceeds at a molecular level is called a reaction mechanism. Determination of reaction mechanisms requires a broad and detailed understanding of the properties of reactants and products and the changes that occur before, during, and after a chemical reaction and is often difficult if not impossible to confirm unequivocally.
A study on isothermal reduction kinetics of titaniferous magnetite ore using coke dust, an industrial waste
Published in Canadian Metallurgical Quarterly, 2019
Bitan Kumar Sarkar, Maharshi Ghosh Dastidar, Rajib Dey, Gopes Chandra Das
The study of reaction kinetics is necessary to know the underlying reaction mechanism(s) as well as the activation energy associated with the reaction(s). These informations are vital for control of the reactions [21–25]. The study of the reduction kinetics of the Bama ilmenite and graphite has been carried out by thermogravimetry analysis in the temperature range of 850–1400°C [26]. It was concluded that a chemical reaction mechanism was dominant below 1100°C, while mixed mechanism of chemical controlled and diffusion dominated over the temperature range of 1100–1250°C. Furthermore, diffusion controlled mechanisms were operative above 1250°C. Kowitwarangkul et al. [27] have reported that there is a possibility to decrease the thermal reserve zone temperature and reductant rate in Blast Furnace by using the self-reducing pellets (SRP) which consists of iron ore fines and solid carbonaceous reducing agents like coal, coke and charcoal. They have also studied the isothermal and non-isothermal kinetics of reduction of SRP. In our previous publication [28], reduction kinetics of self-reducing briquettes of titaniferous magnetite ore (TMO) and lean grade coal has been studied and mixed kinetic model (CG3 at the beginning and D4 in the later part of the reduction) has been identified as the driving mechanism.