Thermodynamics the Second Law

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

Second Law of Thermodynamics The Second Law of Thermodynamics states that all processes that occur spontaneously move in the direction of an increase in entropy of the universe (system + surroundings). 

Ions or molecules flowing down their concentration gradients is one aspect of a very general statement known as the Second Law of Thermodynamics. The Second Law is a mathematical statement to the effect that all real processes increase the disorder, captured in a quantity known as entropy, of the universe. Entropy is a measure of disorder or randomness and may be thought of as negative information. 

These two laws can be combined for a system involving only pressure-volume work to obtain dU = TdS — PdV This so-called fundamental equation shows two things (1) thermodynamic properties of a system obey the rules of calculus and (2) the choice of independent variables (in this case S and V) plays a very important role in thermodynamics. The second law can be used to show that when S and V are held constant, the internal energy U of a system must decrease... 

The Carnot cycle engine is actually the only reversible engine that we can design with two heat reservoirs. We see that because of the need to reject heat when returning the engine to its initial state, the engine cannot operate with unit efficiency. In Chapter 3, we will elevate this observation to one of the basic tenets of thermodynamics—the second law. 

Electrochemical reactor design is ideally a good compromise between capital and power costs. The power consumption of a cell or reactor is the most important single factor needed to evaluate its performance. Both the powar production and chemical process industries, (CPI), involve heat and electrical energy in a similar fundamental way, and so are governed by the second law of thermodynamics. The second law actually imposes an absolute natural limitation on the efficiency of any energy transformation, and therefore it provides a reliable standard with which to compare and control practical operations (30) (31) (32). 

Lord Kelvin was bom WiUiam Thomson (1824- 1907), British physicist and mathmiaUcian, ja-ofessor at the University of Glasgow. His main contributions are in thermodynamics (the second law, internal energy), theory of electric oscillations, theoy of potentials, elasticity, hydrodynamics, etc. His great achievements were honored by the title of Lord Kelvin in 1892. 

In general, any irreversible process results in an increase in the entropy of the universe, whereas any reversible process results in no change in the entropy of the universe, a statement known as the second law of thermodynamics. The second law of thermodynamics can be expressed in terms of either of the following two equations ... 

In classical thermodynamics, the Second Law consists of two parts (see Kestin 1979). The first part defines the entropy for reversible processes based on Carathdodory s theorem. The latter part concludes that entropy increases in all irreversible processes. Recall that, as discussed in Sect. 3.1, the terminologies of the reversible and irreversible processes are used here in the sense of classical thermodynamics however, in this Section irreversible processes acquire a different interpretation to that used in the classical sense. That is, we may be able to introduce an apparent irreversible process for the case that considers a non-measurable energy, which will be discussed in more detail in Sect. 3.3.2. 

Note 3.4 (On the constitutive relation and the Second Law of Thermodynamics). The Second Law of Thermodynamics essentially gives a relationship between the heat flux q that is externally supplied and the induced temperature field. Some scientists have stated that constitutive relations that depend on fields other than the temperature can also be derived by the Second Law however, as shown above, the Second Law does not consider fields other than the heat flux and temperature. All the constitutive relations can be derived from the First Law of Thermodynamics, internal energy and thermodynamic potentials induced by Legendre transformations (see Sect. 3.4). ... 

In non-equilibrium thermodynamics, the second law is reformulated using the local entropy production in the system, cr, which is given by the product sum of the so-called conjugate fluxes, and forces, A, in the system. Using the assumption of local equilibrium, the second law becomes... 

The limitation on the convertibility of heat to work that Carnot discovered is one manifestation of a fundamental limitation in all natural processes it is the Second Law of thermodynamics. The Second Law can be formulated in many equivalent ways. For example, as a statement about a macroscopic impossibility, without any reference to the microscopic nature of matter ... 

Thermodynamics It deals with the transformation of energy from one form to another (EB is an expression of the first law of thermodynamics). The second law states that in a process of heat transfer alone, energy may be transferred only from higher T to a lower T. 

Like the first law of thermodynamics, the second law is a postulate, based on experience and cannot be proved. The second law formed the basis for treating the concept of equilibrium within physical chemistry. In this chapter the second law is introduced along with the use of the concept of equilibrium their applications are illustrated by practical problems within the science of construction materials. 

We shall see that the diffusion coefficient for bulk diffusion is indeed a function of pressure, temperature, molecular size, and weight. Diffusion is a spontaneous process that is a result of the second law of thermodynamics. The second law of thermodynamics requires that thermodynamic processes proceed in a way that maximizes entropy. This ultimately requires uniform mixing of everything in the universe. When there is nonuniform mixing, diffusion occurs to eliminate concentration gradients and can be written as... 

The equilibrium condition Q = K is a thermodynamic result, obtained in Chapter 13 by applying the laws of thermodynamics (the second law, in particular). The thermodynamic equilibrium condition is indeed very useful— as we will soon see— but it does not account for the following observation about the equilibrium condition ... 

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