Equilibrium processes definition

All acid-base abnormalities result from underlying disease processes. Definitive therapy for these disturbances requires treatment of the illness that has disrupted the pH equilibrium. 

One could go on with examples such as the use of a shirt rather than sand reduce the silt content of drinking water or the use of a net to separate fish from their native waters. Rather than that perhaps we should rely on the definition of a chemical equilibrium and its presence or absence. Chemical equilibria are dynamic with only the illusion of static state. Acetic acid dissociates in water to acetate-ion and hydrated hydrogen ion. At any instant, however, there is an acid molecule formed by recombination of acid anion and a proton cation while another acid molecule dissociates. The equilibrium constant is based on a dynamic process. Ordinary filtration is not an equilibrium process nor is it the case of crystals plucked from under a microscope into a waiting vial. 

By comparing these constants with the equilibrium constants of anion-radical reactions (entries 7-10 in Table 2.1), one can conclude that in case of dianions, the equilibrium is definitely shifted to the right. The equilibrium constants of ca. 0.35 are increased almost twofold, up to approximately 0.7, but remain less than unity. This means that even with the formation of dianions, the possibility of isotopic enrichment still remains qnite feasible, although the process becomes less favorable than that in the case of nitrobenzene. 

Thermo-reversible has the following meaning if an amorphous polymer is heated to above Tg, it readily reaches thermodynamic equilibrium by definition the sample has then "forgotten" its history, any previous ageing it may have undergone below Tg having been erased. In other words it is completely rejuvenated. Ageing therefore is a thermo-reversible process to which one and the same sample can be subjected an arbitrary number of times. It has just to be retreated each time to the same temperature above Tg. 

In the theory of non-equilibrium processes at solid state junction and also semiconductor-liquid interfaces, as developed in the previous section, frequently quasi-Fermi levels have been used for the description of minority carrier reactions [90, 91], A concept for a quantitative analysis for reactions at n- and p-type electrodes has been derived [92, 93], using the usual definition of a quasi-Fermi level (Eqs. (3a) and (3b)). Taking a valence band process as an example, the quasi-Fermi level concept can be illustrated as follows ... 

The basics of general acid and general base catalysis are described clearly and in detail in Chapter 8 of Maskill [1]. Acid-base catalysis is termed specific if the rate of the reaction concerned depends only on the acidity (pH, etc.) of the medium. This is the case if the reaction involves the conjugate acid or base of the reactant preformed in a rapid equilibrium process - normal behavior if the reactant is weakly basic or acidic. The conjugate acid or base is then, by definition, a strong... 

Before we discuss the next major definition of acid-base behavior, let s examine a crucial property of water that enables us to quantify [H30 J in any aqueous system water is an extremely weak electrolyte. The electrical conductivity of tap water is due almost entirely to dissolved ions, but even water that has been repeatedly distilled and deionized exhibits a tiny conductance. The reason is that water itself dissociates into ions very slightly in an equilibrium process known as autoionization (or self-ionization) ... 

Concrete definition of equilibrium state must be performed for each constitutive model (characterized by the observer s scales of Sect. 1.1 and mainly Sect. 2.3) by time fixing of some quantities from those determining their states (see Rem. 6). Time persistency is usually difficult to achieve (because of molecular fluctuation) and therefore to describe real materials by such constitutive models we must add to constitutive equations (as their regularity) the conditions of stability by which the time permanence of equilibrium state S4 is assured. For details see Sects. 2.1-2.4, 3.8, 4.7 and Rems. 7,9, 11 in Chap. 2. Although one eqrulibrium state would suffice, typically there are more equilibrium states often forming the equilibrium process as their time sequence, see Rem. 12. 

Therefore C is the set of w, Q of the cyclic reversible and homogeneous processes starting in equilibrium (see definitions above with a = —I meaning reversibility and a > 0 meaning homogeneity respectively). 

Even this reversible process is rather a special one. We note it here to demonstrate that in the model of the linear fluid equality (in entropic inequality) is possible, see (1.35), and to show that entropy may be calculated with the precision of a constant, see (1.40), cf. application of reversible processes in Sect. 1.4. An equilibrium state is also an equilibrium process formed by a unique state with (3.231), cf. definition below (2.11). 

Definition of equilibrium is motivated similarly as in Sects. 1.2, 2.1, 2.2 and 3.8 [39, 52, 53, 56, 79, 98, 142, 143] (for non-linear models, see, e.g. [60, 71, 72]). For the regular linear fluid mixture model summarized at the end of previous Sect. 4.6, we define equilibrium by zero entropy production (4.301) as an equilibrium process going persistently through a unique equilibrium state, which is possible, as we shall see, if the body heat source is zero (4.303) and at zero rates of chemical reactions (4.302). By regularity conditions (see 1,2,3 at the end of Sect. 4.6), we exclude some unusual processes compatible with zero entropy production. We apply the regularity conditions on equilibrium states (moreover, regularity condition 3 follows for stable equilibrium states which will be discussed later in this Sect. 4.7). 

This definition of the equilibrium process has the following consequences in equilibrium it follows from (4.301) and (4.168) that... 

Kedem ° attempted to circumvent the paradox implicit in the driving of vectorial transport processes with supposedly scalar chemical forces by introducing a vectorial cross coefficient in a non-equilibrium thermodynamic definition of active transport. Jardetzky , however, stated that the direct coupling between a metabolic reaction and a transport process, implied by Kedem s vectorial cross coefficient, was impossible because it would contravene the Curie principle (see also ref. 11). Katchalsky and Kedem, later supported by Moszynski et al, answered the criticism of Jardetzky by saying that Langeland had shown that the principle of Curie applies... 

Before we discuss the next major acid-base definition, let s examine a crucial property of water that enables us to quantify [H3O+] water dissociates very slightly into ions in an equilibrium process known as autoionization (or self-ionization) ... 

This chapter limits itself to P-NMR studies on phospholipids and lysophospholipids in monomeric and micellar states and focuses on the identification of species and aggregation states, as well as on the dynamic processes of migration and reaction kinetics. For this purpose, micelles and mixed micelles are defined as dilute isotropic solutions of phospholipids, either with or without detergents that form spontaneously and are at thermodynamic equilibrium diis definition specifically excludes sonicated or small unilamellar vesicles as well as membranes. These are covered by Smith and Ekiel (Chapter 15). This limitation in scope necessarily requires heavy reliance on work from the laboratory of the authors of this chapter. 

The thennodynamic process is referred to as reversible if a thermodynamic system passes through the same intermediate equilibrium states in both the forward and in the opposite direction but in the reverse sequence additionally, there will be no change in the surrounding bodies. It follows from this definition that any equilibrium process is reversible. Any process that does not meet these requirements is irreversible. 

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