Irreversible reaction, definition

Irreversible reaction, 1251, 1419 Isoconic, definition, 933, 978, 982 Isotherm, 932, 964, 1197 applicability, 941 and charge transfer, 954, 955 Conway and Angersein-Kozlowska, 943 definition, 933 in electrode kinetics, 1197 Flory—Huggins type, 941,942, 944, 965 Frumkin, 938, 942, 965 Frumkin-Temkin, 1197, 1198 Habib-Bockris, 943... 

O Brien. 1235 Ohmic drop, 811, 1089, 1108 Ohmic resistance, 1175 Ohm s law, 1127. 1172 Open circuit cell, 1350 Open circuit decay method, 1412 Order of electrodic reaction, definition 1187. 1188 cathodic reaction, 1188 anodic reaction, 1188 Organic adsorption. 968. 978. 1339 additives, electrodeposition, 1339 aliphatic molecules, 978, 979 and the almost-null current test. 971 aromatic compounds, 979 charge transfer reaction, 969, 970 chemical potential, 975 as corrosion inhibitors, 968, 1192 electrode properties and, 979 electrolyte properties and, 979 forces involved in, 971, 972 977, 978 free energy, 971 functional groups in, 979 heterogeneity of the electrode, 983, 1195 hydrocarbon chains, 978, 979 hydrogen coadsorption and, 1340 hydrophilicity and, 982 importance, 968 and industrial processes, 968 irreversible. 969. 970 isotherms and, 982, 983... 

In words when a system undergoes a change, the increase in entropy of the system is equal to or greater than the heat absorbed in the process divided by the temperature. On the other hand, the equality, which provides a definition of entropy increment, applies to any reversible process, whereas the inequality refers to a spontaneous (or irreversible) process, defined as one which proceeds without intervention from the outside. Example 1 illustrates the reversible and irreversible reactions. 

Other important definitions include those of homogeneous, heterogeneous, and irreversible reactions. A homogeneous reaction occurs within a single phase, as in a stream that is, + HCOj = H2CO3. Heterogeneous reactions occur between phases, as gas-water, water-mineral, or, rarely, gas-mineral, as illustrated by the following reactions... 

These results show that the first-order curves in Fig. 11-7 can be used for reversible as well as irreversible reactions, provided in the definition of s or is replaced by... 

Type I. For parallel reactions with separate reactants, the analysis is easily handled, since the two steps are independent of each other. Indeed, the inclusion of Type 1 as a nearly complex scheme is not really necessary for the homogeneous batch reactions at constant volume treated here, since the yield and selectivity definitions are redundant in this case with rate and conversion. The system is important in heterogeneous systems, however, so we introduce it for later reference. For first-order, irreversible reactions ... 

One addition to the assembly lexicon added a layer of complexity to the above definition. Thus, one of the seven different classes of self-assembly originally proposed by Lindsey. — which are strict self-assembly processes (with or without a template) positioned in different chemical settings—is commonly known as "irreversible self-assembly." This term is used to describe two-step processes, whereby a strict self-assembly processes is followed by irreversible reactions that covalently knit together the array of subunits. As Whitesides noted, strictly speaking this term is a misnomer. Hence, along with other types of post-assembly modified self-assemblies, we categorize these processes as "self-assembly with covalent modification." Postmodification generally comes in the form of a series of covalent bond formation steps and is of less interest to us here. The crux of any self-assembly process is the self-assembly. 

Unfortunately, life is not quite that simple. The Thiele modulus contains some variables that influence the rate, even if rj = 1. Recall the definition of

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We will see that kaolinite Al2(Si205)(0H)4 - which is the main mineral of clays, hence the name kaolin given to some clays rich in kaolinite - undergoes irreversible reactions that transform it into metakaolinite when it is fired above approximately 500°C, which could justify the temperamre of 540°C selected in the definition used to make the distinction between dried earth and terra cotta. 

This definition for reaction order is directly meaningful only for irreversible or forward reactions that have rate expressions in the form of Equation (1.20). Components A, B,... are consumed by the reaction and have negative stoichiometric coefficients so that m = —va, n = —vb,. .. are positive. For elementary reactions, m and n must be integers of 2 or less and must sum to 2 or less. 

Several descriptions of electrode reaction rates discussed on the preceding pages and the difficulty to standardize electrode potential scales with respect to different temperatures imply several definitions of activation energies of electrode reactions. The easiest way to determine this quantity, for example, for an irreversible cathodic process, employs Eqs (5.2.9), (5.2.10) and (5.2.12) at a constant electrode potential,... 

Definition of symbols AEp = peak potential difference, Epa = peak potential at cathodic peak current, Epc = peak potential at anodic peak current, tpa = anodic peak current, ipc = cathodic peak current, s = scan rate, t = time after peak (the Cottrell region), n = number of electrons involved in redox reaction. Rate parameters (acn ) and heterogeneous rate constant can be found from irreversible wave. 

Many electrochemical studies on Cu(II/I) systems exhibit irreversible or quasi-reversible behavior or involve coupled chemical reactions. There are no known examples of Cu(II/I) systems where irreversibility can be definitively attributed to slow electron transfer. However, many... 

For definiteness let the two reactions be simple but the second irreversible, so that... 

The enthalpy 7, besides a pair of variables determining the physical state of the material (e.g., p and S or p and v), also depends on the chemical variable n—the depth of occurrence of the irreversible chemical reaction which, for definiteness, we will equate with the concentration (dimensionless, g/g) of the final reaction product. It should be kept in mind that the reaction occurs, particularly at the beginning, irreversibly. 

By definition chirality involves a preferred sense of rotation in a three-dimensional space. Therefore, it can only be affected by a modification of the nonscalar fields appearing in the rate equations. For a reaction-diffusion system [equations (1)] these fields are descriptive of a vector irreversible process, namely, the diffusion flux J of constituent k in the medium. According to irreversible thermodynamics, the driving force conjugate to diffusion is... 

ESCA results for double promoted oxides are less definitive than those previously described, but definitely show differences in the Si 2p spectra, hence indicating that again surface changes are occurring due to the irreversible surface chemical reactions. At the same time, these oxide surfaces are being at least partially cleaned of C/O-containing atmospheric contaminants. 

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