Endothermic process entropy changes

FIGURE 7.17 (a) In an exothermic process, heat escapes into the surroundings and increases their entropy, (b) In an endothermic process, the entropy of the surroundings decreases. The red arrows represent the transfer of heat between system and surroundings, and the green arrows indicate the entropy change of the surroundings. 

This is a strongly endothermic process, but it becomes possible at high temperature due to a favorable entropy change - formation of the random vapor state from solid reactants. Such reactions provide another reason for the lower flame temperatures achieved when organic binders are added to oxidizer/metal mixtures [3]. 

G decreases for a spontaneous process, like the energy of a mechanical system. Since AG incorporates both driving forces for spontaneity—enthalpy (energy) decrease and entropy (disorder) increase—an endothermic process may be spontaneous if the increase in disorder is big enough to counteract the unfavorable enthalpy change, and a process that leads to increased order (negative AS) may be spontaneous if the process is sufficiently exothermic (negative AH). 

Why, then, does a solution ever form You may recall from general chemistry that whether a reaction is spontaneous or not depends on both the enthalpy and the entropy of that process. Entropy (S) is a measure of disorder. Processes that increase the disorder in a system (AS > 0) are favored. Although most solution processes are endothermic (disfavored by enthalpy, AH > 0), the solution is more disordered than the separate solute and solvent (favored by entropy, AS > 0). Therefore, as long as the process is not too endothermic, the favorable entropy change will cause the solute to dissolve. Whether the process is likely to be too endothermic can be estimated by examining the... 

The lattice enthalpy for crystal formation is large enough to overcome all the endothermic processes (and the negative entropy change) and to make formation of LiF from the elements a very favorable reaction. 

A sugar cube dissolves in a cup of coffee in an endothermic process, (a) Is the entropy change of the system (sugar plus coffee) greater than, less than, or equal to zero ... 

How does the entropy of the surroundings change during an exothermic reaction An endothermic reaction Other than the examples cited in text, describe a spontaneous endothermic process. 

A detailed analysis of different contributions to the enthalpy and entropy changes, for a number of protein-adsorbent systems, was carried out by Norde. Lyklema, and others 117,103,118,119], They showed that the protein adsorption on solids is often endothermic and that the driving force of the process is the positive ASaiis. The main contributions to large positive values of entropy can arise from sorbent surface dehydration and from the conformational rearrangement of protein molecules upon adsorption [17]. 

Dissociation of reactant A is an endothermic process in which the entropy change is positive. Consequently, the equilibrium constant increases at higher temperature via Le Chatelier s principle, which shifts the reaction to the right in favor of... 

The reaction enthalpy A// is negative in exothermic processes, and positive in endothermic processes. The reaction entropy AS, which is a measure of the change in the state of disorder of the system, is always positive since the entropy of the solution (mixture) is always greater than that of the pure components. 

The negative Gibbs free energies show spontaneous adsorption process and the decreasing value by rising temperature indicate the physical nature adsorption. By plotting nk versus 1/T, the enthalpy and entropy change can be obtained. A positive value of enthalpy indicates an endothermic process and vice versa. Most adsorption processes are spontaneous with minor exceptions. 

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