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Chemical Thermodynamics and Thermochemistry
Published in Armen S. Casparian, Gergely Sirokman, Ann O. Omollo, Rapid Review of Chemistry for the Life Sciences and Engineering, 2021
Armen S. Casparian, Gergely Sirokman, Ann O. Omollo
As a second component of thermodynamics, entropy is a measure of the statistical disorder or randomness of a system. The universe tends to move toward greater total disorder, and this is expressed in terms of entropy or S. Entropy, unlike enthalpy, can be found explicitly. Entropy specifically is a measure of the number of microstates available to a chemical system. Microstates are individual possible states of the system, where a state is a particular arrangement of positions for particles and a particular distribution of kinetic energy among those particles. This can be calculated as shown in Equation 5.6, where S is the entropy, k is Boltzmann’s constant, and W is the number of available microstates. S=klnW
Battery Energy Storage
Published in Iqbal Husain, Electric and Hybrid Vehicles, 2021
In galvanic devices, stable substances react spontaneously to form new substances, which mean that the reaction can only go from a higher energy state to a lower one according to the First Law of Thermodynamics. The lower energy state that the substances will assume depends on another measure known as the entropy of a substance. Entropy is a measure of the disorder level for the particles (molecules, atoms, etc.) that make up a substance. Entropy is a property that is specified for every equilibrium state of a substance. Since entropy is a property, the change in entropy in going from one state to another is the same for all processes. The SI unit for entropy is J/K.
Governing equations of fluid motion
Published in Amithirigala Widhanelage Jayawardena, Fluid Mechanics, Hydraulics, Hydrology and Water Resources for Civil Engineers, 2021
Amithirigala Widhanelage Jayawardena
Entropy is defined as the quantitative measure of disorder or randomness in a system. The concept comes out of thermodynamics, which deals with the transfer of heat energy within a system. Instead of talking about some form of ‘absolute entropy’, physicists generally talk about the change in entropy that takes place in a specific thermodynamic process.
Sparse Compression-Based Image Encryption using Data Encryption Standards RC5
Published in IETE Technical Review, 2023
Arghya Pathak, Hrishikesh Mondal, Jayashree Karmakar, Subhashish Pal, Debasish Nandi, Mrinal Kanti Mandal
Entropy is a measure of the randomness of a physical system. The higher is randomness greater the entropy. In the case of an image, entropy is measured to check the irregularity among the pixels of an encrypted image with respect to the original image. For the 8-bit representation of an image, the maximum entropy value can be 8. So, an entropy value closer to 8 ensures better encryption and complexity. The mathematical equation used to calculate information entropy is given by where, e(c) represents the entropy of the cipher image and is the probability of occurrence of . The entropy values of our proposed algorithm for different images are given in Table 4.
Catalytic pyrolysis of algae: kinetics and thermodynamic analysis
Published in Chemical Engineering Communications, 2023
Anjana P. Anantharaman, Chalamala Jaya Prakash, Osipalli Bangarraju, Tamilmani Jayabalan
Entropy is the degree of disorder of the reaction. The range of carbon layers created in the biochar during pyrolysis corresponds to the ΔS value. ΔS value ranges between −8 to 205 J/mol for FWO method, −130 to 95 J/mol for KAS method, and −125 to 100 J/mol for SCR method, respectively. Irrespective of the method adopted, ΔS is low at lower conversion (10 − 40%) and even at higher conversion (80 − 90%); the value is high at the intermediate conversion range of 50 − 70%. The negative ΔS value represents that the thermal equilibrium is attained by changing from a disordered state to a more ordered state. The pyrolysis reaction is reported to show both negative and positive values at different fractional conversions (Shahid et al. 2019; Kong et al. 2022). The average values of ΔS calculated using FWO, KAS, and SCR methods are 81.22, −34.38, and −29.32 J/mol, respectively. In comparison, the ΔS evaluated using FWO method is higher than that of KAS and SCR method which is in same trend with the ΔG reported earlier and the pre-exponential factor calculated using these methods. Lower value of ΔS represents the biomass modifies and moves closer to the thermodynamic equilibrium, and higher value corresponds to high reactivity since the system is far from thermodynamic equilibrium (Açıkalın and Gözke 2021).
Eigenvalues and thermal properties of the A1Σ u + state of sodium dimers
Published in Molecular Physics, 2022
Ridha Horchani, Nidhal Sulaiman, Safa Al Shafii
Entropy is a measure of the probability or disorder of a particular system. It is also the measure of the irreversible changes in the system. In many domains, it is a very useful quantity due to its many applications, including dissolution [49–51], fluorescence microscopy [52], adsorption [53–57], synthesis of materials [58], phase transition [59,60], and protein activity [61–63]. Calculating the molar entropy of a gaseous substance remains a challenging task in science. It is given by where is Avogadro’s number, is Boltzmann’s constant, is the temperature and is the partition function.