The second and third laws of thermodynamics

Practice Problem For each of the following processes, determine the sign of AS (a) crystallization of sucrose from a supersaturated solution, (b) cooling water v ror from 150°C to 110°C. (c) sublimation of dry ice. 

1 For which of the following physical processes is AS negative (Select all that apply.) 

According to the second law of themwdynamics, the entropy of the universe increases in a spontaneous process and remains unchanged in an equilibrium process. Mathematically, the second law of thermodynamics is expres.sed as follows  

The second law of thermodynamics has historically been a mysterious concept, and the basic idea has been verbalized by Clausius, Kelvin, Planck, and others for those who think in words. One simple statement by Rudolph Clausius (1822-1888) was 

Heat generally cannot flow spontaneously from a material at lower temperature to a material at higher 

FIGURE 5.2 A qualitative sketch of the Carnot cycle. The actual shape is more of a narrow crescent shape than is often depicted in other sources. Photographs of Carnot s notes show the graph narrow as shown here. An excellent simulation can be found on the Internet at http / demonstrations.wolfram.com/ CamotCy cleOnldealGas / 

---

The second and third laws of thermodynamics The second law and the definition of entropy... 

The heats of dissociative evaporation of antimony and bismuth tellurides, calculated using the second and third laws of thermodynamics, are in good agreement. This shows that the suggested dissociative evaporation schemes predominate in the investigated temperature intervals. According to [1], the dissociative process... 

Although the mathematical and conceptual tools provided by the zeroth and first laws of thermodynamics are very useful, we need more. There is a major question that these laws cannot answer Will a given process occur spontaneously Nothing in the previous chapters addresses spontaneity, which is an important concept. Thermodynamics helps to understand the spontaneity of processes—but only once we add more of its tools. These tools are called the second and third laws of thermodynamics. 

In this chapter, we show that spontaneous processes are ones in which the entropy of the universe (system and surroundings) increases, and that for reversible processes, the total entropy change of the universe is zero. These conclusions lead us to the second and third laws of thermodynamics. 

The second and third law of thermodynamics can be understood in terms of the disorder concept of entropy. For an isolated system in which there is no transfer of mass or energy, a spontaneous change can be thought of as a change in which the particles of the system access more possible arrangements. That is, for a spontaneous process from state 1 to state 2,... 

The ultimate goal of this work was the calculation of thermodynamic functions, primarily enthalpies and reduced Gibbs energies used in practical calculations, by the second and third laws of thermodynamics. In view of this, the applicability of the procedure used for heat capacity calculations can be estimated by comparing these thermophysical parameters. 

It follows from Tables 284 1 that the convergence of the AsubH°(298, III law) and Asubff°(298, II law) values obtained in our calculations is quite satisfactory. A total of 114 saturated vapor pressure measurements were performed for 14 of the 15 lanthanide trichlorides (all except PmCla). These values were used to calculate the enthalpies of sublimation by the second and third laws of thermodynamics simultaneously. Of these 114 results, 39 were obtained for vapor pressures over solids and 75 for vapor pressures over liquid samples. 

TABLE 60 Enthalpies of sublimation RCI2 (As Jbff°(298), kj/mol) calculated according to the second and third laws of thermodynamics... 

---