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Chemical Reaction Thermodynamics, Kinetics, and Reactor Analysis
Published in Debabrata Das, Debayan Das, Biochemical Engineering, 2019
Equation 3.19 signifies that the quantity of heat transferred is equal to the enthalpy change of a process for a constant-pressure and mechanically reversible process. It is important to now define the two major forms of reactions that largely depend on the positive or negative value of the heat transferred, Q. A reaction that involves heat liberation from the system is known as exothermic reaction. Heat liberation is associated with the negative value of ΔH, and hence for an exothermic process, one can write Q < 0. Combustion reactions are typically exothermic in nature. On the other hand, if heat is absorbed by a system during a reaction, then such a reaction is called an endothermic process. Clearly, an endothermic process involves a positive value of ΔH and that corresponds to Q > 0. When sodium hydroxide is added to water, the system undergoes an absorption of heat, and hence the nature of reaction is endothermic.
E
Published in Splinter Robert, Illustrated Encyclopedia of Applied and Engineering Physics, 2017
[atomic, nuclear, thermodynamics] Chemical or thermodynamic process that requires the addition of heat in order for the process to initiate and proceed. One specific example of an endothermic process is vaporization (see Figure E.56).
Volumetric chemical reactive Casson fluid flow over a nonlinear extended surface
Published in Waves in Random and Complex Media, 2023
Muhammad Shuaib, Muhammad Anas, Hijab ur Rehman
Chemical reaction plays an important role in engineering, industries and biological sciences. There are two types of chemical reactions exothermic and endothermic. In exothermic process of reactions energy is released whilst in endothermic process the energy is observed from the environment. Keeping in view these applications of the chemical reactions Ganesh and Sridhar [24] discussed the effect of chemical reaction towards MHD marginal layer. They found that the increasing values of the chemical reaction decrease the concentration profile. Dharmaiah et al. [25] also concluded the same results, by investigating tha Hall and ion slip impact on magnet-litanium alloy nanoliquids. MHD radiative Casson-Nanofluid stream with chemical reaction through Darcy-Forchiemer medium is examined by Ganesh and Sridhar [26]. Sridhar et al. [27] explore the study of MHD Williamson nanofluid across a permeable medium past an extended sheet. The numerical approach of heat and mass transfer of MHD Casson fluid with chemical reaction is presented by [28–30], they observed that the increasing value of chemical reaction parameter is responsible for the decay in heat transfer rate. The chemical reactions in which the rate of reaction is proportional to the mth order of the concentration reactant is the mth order chemical reaction [31–33].
Lamellar structure silver sulfide nanoparticles for adsorption and selective separation of zirconium, yttrium and strontium ions
Published in Journal of Dispersion Science and Technology, 2022
Hoda E. Rizk, Mohamed F. Attallah, Amal M. Ali
The tabulated data in Table 2 show that the adsorption process is exothermic with ΔH values equal − 41.84 and −16.23 kJ/mol for adsorption of zirconium and yttrium ions, respectively. The change in enthalpy of a reaction is measured by the differences between the enthalpy of the reactants and products. Enthalpy of reactants due to the dehydration of metal ions from their complex is an endothermic process, favored with high temperature; on the other hand, contact of metal ions with the surface of the sorbent is an exothermic process.[52] The negative values of the change in enthalpy for adsorption of Zr(IV) and Y(III) indicate that the energy of attachment of metal ions on the surface of Ag2S exceeds the endothermicity of the dehydration process.
Effect of B-site Zr and Hf substitution on ferroelectric polar order for tetragonal tungsten bronze ceramic
Published in Journal of Asian Ceramic Societies, 2022
Wenbin Feng, Sidi Long, Yi Wan, Dunpu Zhang
The above speculations can be further confirmed by the DSC results and P-E curves of BSHN. It is interesting to find that the entropy of the exothermic process (area circled by the blue curve) is larger than the endothermic process (area circled by the red curve), and the exothermic peak distributes in a wider temperature range. The reason is that theoretically the endothermic entropy is related to the energy difference between the frozen polar regions and the paraelectric phase, while experimentally, when increasing the temperature, the frozen polar region first activate then the polarization rotate to the similar direction, the energy absorbed in this process is hard to detect from the instrument for it is a relaxation process. While the exothermic entropy mainly connects with the energy difference between the disordered paraelectric phase and the ordered ferroelectric phase, and the energy of changing the ordered ferroelectric phase to the low temperature relaxation state. So it is reasonable that the endothermic and exothermic process entropy show large difference.