Enthalpy physical significance

Estimate (a) the specific enthalpy of a 30 wt% H2SO4 solution (aq, TT F) and (b) the specific enthalpy of a 30 wt% solution obtained by mixing pure water at 77°F and pure sulfuric acid at 7T F adiabatically. What is the physical significance of the difference between these two enthalpies ... 

Prom the formal macroscopic statement of the second law of thermodynamics, as developed from classical thermodynamics arguments, it is difficult to assign a physical significance to entropy. Ultimately, you must reassure yourself that entropy is defined mathematically, and like enthalpy, can be used to solve problems even though our physical connexion with the property is occasionally less than satisfying. 

We find cross-sectional area per chain to be a convenient ordering parameter for various (but not all) physical properties such as chain stiffness (a or C ), chain atoms between entanglements, Ng, and enthalpies of activation, for melt flow. The physical significance of such linear correlations is not always apparent. Cross-sectional areas provide an accurate and convenient ordering parameter. 

The adsorption of gases on solids can be classified into physical and chemical adsorption. Physical adsorption is accompanied by a low enthalpy of adsorption, and the adsorption is reversible. The adsorption/desorption characteristics are in these cases often described by adsorption isotherms. On the other hand, chemical adsorption or segregation involves significantly larger enthalpies and is generally irreversible at low temperatures. It is also often accompanied by reconstruction of the surface due to the formation of strong ionic or covalent bonds. 

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