Chemical reactions subscripts

Figure 6.12 uses the term AG°. We might also have used AG and AS. This can cause confusion, unless you refer to Figure 4.12 to see that there is no lexical problem, just a difference in how explicit we wish to be. That is, A G° is just a special case of AG. In this case, we are dealing with a chemical reaction (subscript r ), and with pure phases in their (high T) standard states (superscript °), so A,G° is correct, but AG° or AG is not incorrect. 

Symbols used as subscripts to denote a chemical reaction or process ... 

The formation of the combination of defects may be described as a chemical reaction and thermodynamic equilibrium conditions may be applied. The chemical notations of Kroger-Vink, Schottky, and defect structure elements (DSEs) are used [3, 11]. The chemical reactions have to balance the chemical species, lattice sites, and charges. An unoccupied lattice site is considered to be a chemical species (V) it is quite common that specific crystal structures are only found in the presence of a certain number of vacancies [12]. The Kroger-Vink notation makes use of the chemical element followed by the lattice site of this element as subscript and the charge relative to the ideal undisturbed lattice as superscript. An example is the formation of interstitial metal M ions and metal M ion vacancies, e.g., in silver halides ... 

In a balanced chemical equation (commonly called a chemical equation ), the same number of atoms of each element appears on both sides of the equation, chemical equilibrium A dynamic equilibrium between reactants and products in a chemical reaction, chemical formula A collection of chemical symbols and subscripts that shows the composition of a substance. See also condensed structural formula empirical formula,- molecular formula structural formula. 

Consider the case when the equilibrium concentration of substance Red, and hence its limiting CD due to diffusion from the bulk solution, is low. In this case the reactant species Red can be supplied to the reaction zone only as a result of the chemical step. When the electrochemical step is sufficiently fast and activation polarization is low, the overall behavior of the reaction will be determined precisely by the special features of the chemical step concentration polarization will be observed for the reaction at the electrode, not because of slow diffusion of the substance but because of a slow chemical step. We shall assume that the concentrations of substance A and of the reaction components are high enough so that they will remain practically unchanged when the chemical reaction proceeds. We shall assume, moreover, that reaction (13.37) follows first-order kinetics with respect to Red and A. We shall write Cg for the equilibrium (bulk) concentration of substance Red, and we shall write Cg and c for the surface concentration and the instantaneous concentration (to simplify the equations, we shall not use the subscript red ). 

The reaction is exothermic and the enthalpy change AH° is therefore negative. The heat of reaction —AH° is positive. The superscript ° denotes a value at standard conditions and the subscript r implies that a chemical reaction is involved. 

The total number of atoms on one side of the equation must balance the total number of atoms on the other side. This rule is simply an expression of the well-known chemical fact that atoms are neither created nor destroyed during a chemical reaction. Remember that subscripts and superscripts are labels describing charges and sites and are not counted in evaluating the atom balance. 

We will generally not be concerned here with chemical reactions, so the Ri term can be omitted, in which case the subscript i denoting species is no longer required. In addition, for the turbulent flows of interest the molecular diffusion term in Eq. (2.1) may be neglected. [Although for the spatial scales of interest to us the molecular diffusion term may be neglected, molecular and turbulent diffusion are not independent, linearly additive, physical processes (Saffman, I960).] As a result of the above two simplifications, Eq. (2.1) becomes... 

Chemical reactions are designated as C, so if the product of electron transfer undergoes a homogeneous chemical reaction we say that it is an EC reaction. The C terms are often given a superscript or subscript to show why type of chemical reaction occurs, e.g. disproportionation, dimerization or catalytic. Table 6.4 lists many of the commonly encountered Reinmuth terms. 

We will indicate the order of the chemical reaction with a subscript, so k2 is the rale constant of a second-order reaction. 

Most often, we are not interested in the "absolute" value of H, but rather in its change, AtrH. The subscript "tr" refers to the nature of the change. If the change involves temperature and/or pressure for a one-phase system only, no subscript is used for A. But in case of a phase transition, of mixing, or of a chemical reaction, the subscript is used and may read "vap" for vaporization, "mix" for mixing, or "r" for reaction, and so forth. 

Each of the reactions (r) contributing to the overall metabolic activity has a characteristic molar enthalpy, A,//b (J moL1), where subscript B indicates that any given reaction stoichiometry must be divided by vB (v = stoichiometric number) to give a stoichiometric form of unity (IVbI = 1). Each is calculated from the balanced reaction stoichiometry and enthalpy of formation. If this value is multiplied by the measured chemical reaction flux, JB (mol s 1 m-1), then the reaction enthalpy flux, JhO mo -3), is obtained,... 

To express the heat absorbed or evolved in any chemical reaction, the symbol AH°S is used in which the superscript 0 indicates a standard state and the subscript specifies the temperature at which the reaction occurs. The standard state for a gas is 1 atm pressure and the standard state for liquids is the pure liquid under the same conditions. For solids, it refers customarily to a crystalline state at 1 atm. Unless otherwise denoted, 25°C is the standard state for temperature. 

In the same way, you can recognize similarities between chemical reactions and the types of reactants that tend to undergo different types of reactions. With this knowledge, you can predict what will happen when one, two, or more substances react. In this section, you will often see chemical reactions without the subscripts showing the states of matter. They are omitted deliberately because, in most cases, you are not yet in a position to predict the states of the products. 

The subscript r is used to denote changes associated with a chemical reaction. Although symbols such as ArH should denote the integral enthalpy of reaction, ArH = H( 2) — H( i)> in practice this symbol is usually used to denote the change divided by the amount transferred, i.e. the change per extent of reaction, defined by the equation... 

Note that rB and v can also be defined on the basis of partial pressure, number concentration, surface concentration, etc., with analogous definitions. If necessary differently defined rates of reaction can be distinguished by a subscript, e.g. vp = vB 1dpB/dt, etc. Note that the rate of reaction can only be defined for a reaction of known and time-independent stoichiometry, in terms of a specified reaction equation also the second equation for the rate of reaction follows from the first only if the volume V is constant. The derivatives must be those due to the chemical reaction considered in open systems, such as flow systems, effects due to input and output processes must also be taken into account. 

We represent the net change of a thermodynamic parameter in a chemical reaction by, say, AG and individual component by subscripted letters. 

An unbalanced chemical equation is of limited use. Whenever you see an equation, you should ask yourself whether it is balanced. The principle that lies at the heart of the balancing process is that atoms are conserved in a chemical reaction. The same number of each type of atom must be found among the reactants and products. Also, remember that the identities of the reactants and products of a reaction are determined by experimental observation. For example, when liquid ethanol is burned in the presence of sufficient oxygen gas, the products will always be carbon dioxide and water. When the equation for this reaction is balanced, the identities of the reactants and products must not be changed. The formulas of the compounds must never be changed when balancing a chemical equation. That is, the subscripts in a formula cannot be changed, nor can atoms be added or subtracted from a formula. 

Another example where the second portion of a string subscript is the reason for existence of the type of mass involved is Mcaocauco,- In this symbol, Ca(HC03)2 is the reason for the existence of CaO. In the pertinent chemical reaction, calcimn... 

To investigate this problem, let the radii of the inner and outer tubes be a and b, respectively. We shall denote the species in the inner and outer tubes by the subscripts F and O, respectively, and shall consider the one-step overall chemical reaction... 

---