This study focused on the thermal decomposition of biomineralized CaCO 3 , using avian eggshell. Biomineralized CaCO 3 , which exhibits a specialized structure, is a possible source of CaO used across various applications, including CO 2 capture. An understanding of the relation between the thermal decomposition kinetics in producing CaO and the original structure of biomineralized CaCO 3 may contribute to the further effective use of biowastes. The thermal decomposition of avian eggshell occurs via two mass-loss processes: the primary thermal degradation of the outer shell membrane and the subsequent thermal decomposition of calcite in the shell matrix. Each mass-loss process is composed of multiple reaction steps. The partially overlapping reaction steps originate from the structural characteristics of the eggshell, in addition to the physicochemical properties of the reactant in each process. The overlapping features of the component reaction steps were revealed by a detailed kinetic analysis of mass-loss curves, thus determining the contribution and kinetic parameters of each reaction step. The separated reaction steps were correlated with the corresponding reaction region in the eggshell structure by observing morphological changes during the reaction. Spatially, the morphological characteristics of the as-produced CaO varied markedly, that may indicate a variety of functionalities in terms of material use.

This study focuses on designing a laboratory learning program for a high school chemistry course in which students could discover the fundamental principles of Hess's law via stepwise inquiry. By exploring the chemical properties of common desiccants, mainly those that were reactive in water, students were introduced to the exothermic reaction of CaO(s) with H 2 O(l) as a heating agent. Due to the difficulties associated with directly measuring the heat of reaction for CaO(s) with H 2 O(l), the heats of reaction for CaO(s) with HCl(aq) and Ca(OH) 2 (s) with HCl(aq) were measured. Students could find the most appropriate experimental procedures through discussion in each group and subsequently establish a protocol in the class. The heats of reaction determined by students' experiments closely corresponded to those calculated using the thermodynamic database. Using the experimental values obtained for the reactions of CaO(s) with HCl(aq) and Ca(OH) 2 (s) with HCl(aq), students could discover the relationship that existed among the heats of reaction for CaO(s) with H 2 O(l), CaO(s) with HCl(aq), and Ca(OH) 2 (s) with HCl(aq) by drawing an energy diagram and making the relevant thermochemical calculations.

This article demonstrates a kinetic approach to partially overlapping multistep chemical reactions in solid-gas systems as exemplified by the thermal decomposition of granular sodium perborate tetrahydrate. This reaction proceeds via successive thermal dehydration and decomposition occurring at different temperatures to form sodium metaborate. Each reaction process comprises several kinetic steps originating from different physicochemical and physico-geometric phenomena. The partially overlapping multistep processes were characterized using available thermoanalytical techniques and microscopic observations. Conventional isoconversional kinetic analysis and empirical mathematical deconvolution were applied to each reaction process as preliminary kinetic approaches to extracting provable kinetic information. Then, each reaction process was analyzed kinetically based on a cumulative kinetic equation, i.e., kinetic deconvolution analysis. The results of the kinetic deconvolution analysis were further examined by comparison with other kinetic information for the specific kinetic steps obtained from different thermoanalytical measurements. From the results of this comprehensive kinetic approach, the kinetic features of the thermal dehydration and decomposition processes were revealed by identifying their contributing physicochemical and physico-geometric phenomena and evaluating their influences on the overall multistep processes.