Equilibrium constant for chemical reaction

Quantity K is the chemical reaction equilibrium constant for reactionyj and AG° is the corresponding standard Gibbs energy change of reaction (eq. 237). Although called a constant, fC is a function of T, but only of T. 

Carnot s equations, 146-147 Carnot s theorem, 142-143 Chemical potential, 298, 302, 303 as equilibrium criterion, 298-299, 503 for ideal gas, 302 for ideal solution, 303 Chemical reaction equilibrium constant for, 504-516 equilibrium conversion of, 518-528, 533-542 heat effects of, 116-133 reaction coordinate for, 497-501 reversible, 41-42, 505-507 standard property changes for, 125, 505 stoichiometry, 497-501... 

Once the chemical reaction equilibrium constant (for a particular reaction) has been determined, one can proceed to estimate the quantities of the participating species at equilibrium. The problem that remains is to relate K to understandable physical quantities. For gas-phase reactions, as in an incinerator operation, the term K may be approximately represented in terms of the partial pressures of the components involved. This functional relationship for the hypothetical reaction... 

The chemical-reaction equilibrium constant for this reaction is written as ... 

The Equilibrium (Mass Action) Expression Gas Phase Equilibria Kp vs. Kp Homogeneous and Heterogeneous Equilibria Numerical Importance of the Equilibrium Expression Mathematical Manipulation of Equilibrium Constants Reversing the Chemical Equation Adjusting the Stoichiometry of the Chemical Reaction Equilibrium Constants for a Series of Reactions Units and the Equilibrium Constant... 

Solubility equihbrium is the final state to be reached by a chemical and the subsurface aqueous phase under specific environmental conditions. Equihbrium provides a valuable reference point for characterizing chemical reactions. Equilibrium constants can be expressed on a concentration basis (/ ), on an activity basis (K ), or as mixed constants (K" ) in which all parameters are given in terms of concentration, except for H, OH", and e" (electron) which are given as activities. 

The standard free energy of reaction AG° may be calculated from standard free energy of formation data in a manner similar to that for the standard enthalpy of reaction. The following equation is used to calculate the chemical reaction equilibrium constant AT at a temperature F ... 

Refer to Problem THR. 10. The chemical reaction equilibrium constant based on partial pressures (Kp) was obtained as a function of temperature for the reaction... 

SIT ion interaction coefficient between substance B and substance 62 stoichiometric coefficient of substance B (negative for reactants, positive for products) stoichiometric coefficient general equation for a chemical reaction equilibrium constant... 

The relatively large valons found for the extraction equilibrium constant of copper with Kelex 100 (3 and 90) indicate (hat shipping of copper from (his rcngenl should he difficult. It is fonnd, however, that copper does strip reedily into sulfuric acid solutions because Kalex 100 reacts with sulhiric acid in preference to copper. Fitting the extinction of sulforic acid by Kelex 100 by a chemical-reaction equilibrium constant. 

Amine-extraction equilibria can also be modeled by chemical-reaction equilibrium constants. Figure 8.3-3 indicates that cations such as iron(IIl), zinc, cobelt(ll) and coppeifU) exhibit high distribution coefficients with chloride solutions, wherese nickel. iron(II), and manganese are not extracted to any great extent. The besis for the differences in distribution coefficients lies mainly in the tendency for the former group of cations to fonn chloride complexes. Stability constants for these complexes are available in the literature,11 and they can be used to develop quantitative phase-equilibrium models. 

When striving for high reactor conversions, it may be necessary to consider the reverse reaction even when the reaction is considered to be irreversible. This is the case for the hydrodealkylation of toluene. A rate equation for the reverse reaction can be derived from the rate equation for the forward reaction, given by Eq. (8.2), by assuming that the two rate equations are consistent with the chemical-reaction equilibrium constant. Assume that the gas reacting mixture is ideal at the high temperature of the reaction. Then, the chemical equilibrium constant can be expressed in terms of concentrations and equated to the ratio of the rate constants by ... 

Chemical reactions for defects can be formulated and treated using the mass-action law. As for other chemical reactions, equilibrium constants can be defined in terms of the activities of the defects and other species. Under the normal constrictions we can approximate activities with concentrations of defects and partial pressures of gases. The equilibrium constants can also be expressed in... 

Equilibrium constants,, for all possible dimerization reactions are calculated from the metastable, bound, and chemical contributions to the second virial coefficients, B , as given by Equations (6) and (7). The equilibrium constants, K calculated using Equation (3-15). 

To proceed fiirther, to evaluate the standard free energy AG , we need infonnation (experimental or theoretical) about the particular reaction. One source of infonnation is the equilibrium constant for a chemical reaction involving gases. Previous sections have shown how the chemical potential for a species in a gaseous mixture or in a dilute solution (and the corresponding activities) can be defined and measured. Thus, if one can detennine (by some kind of analysis)... 

The most important themiodynamic property of a substance is the standard Gibbs energy of fomiation as a fimetion of temperature as this infomiation allows equilibrium constants for chemical reactions to be calculated. The standard Gibbs energy of fomiation A G° at 298.15 K can be derived from the enthalpy of fomiation AfT° at 298.15 K and the standard entropy AS° at 298.15 K from... 

In the previous section we saw how voltammetry can be used to determine the concentration of an analyte. Voltammetry also can be used to obtain additional information, including verifying electrochemical reversibility, determining the number of electrons transferred in a redox reaction, and determining equilibrium constants for coupled chemical reactions. Our discussion of these applications is limited to the use of voltammetric techniques that give limiting currents, although other voltammetric techniques also can be used to obtain the same information. 

Determining Equilibrium Constants for Coupled Chemical Reactions Another important application of voltammetry is the determination of equilibrium constants for solution reactions that are coupled to a redox reaction occurring at the electrode. The presence of the solution reaction affects the ease of electron transfer, shifting the potential to more negative or more positive potentials. Consider, for example, the reduction of O to R... 

If the equilibrium constant for the equation as written is 1 X 10 5, what is the pressure of N204 after 20,000 years Assume that the C02 does not participate in any chemical reactions. 

The determination of ArG° for a chemical reaction is very useful in predicting the course of the reaction. Qualitatively, we will show in Chapter 5 that with ArC°<0, the reaction is spontaneous, at least when products and reactants are in their standard state condition. Quantitatively, we will see in Chapter 9 that ArG° can be used to calculate the equilibrium constant for the reaction, from which the final equilibrium conditions can be determined. 

Measurement of Equilibrium Constants Electrochemical cells can be used to measure equilibrium constants for chemical reactions. For example, consider the cell... 

Where the parenthesis refer to the chemical activities of the reactants and K is the equilibrium constant for the previous equation. Similar considerations apply to the oxidation of less electropositive impurities from the anode when a current is passed through the cell. Thus, for the case of iron impurity in the anode, the reaction... 

If a chemical equation can be expressed as the sum of two or more chemical equations, the equilibrium constant for the overall reaction is the product of the equilibrium constants for the component reactions. For example, consider the three gas-phase reactions... 

The following plot shows how the partial pressures of reactant and products vary with time for the decomposition of compound A into compounds B and C. All three compounds are gases. Use this plot to do the following (a) Write a balanced chemical equation for the reaction, (h) Calculate the equilibrium constant for the reaction, (c) Calculate the value of Kc for the reaction at 25°C. 

Cyclohexane (C) and methylcyclopentane (M) are isomers with the chemical formula C6H12. The equilibrium constant for the rearrangement C M in solution is 0.140 at 25°C. (a) A solution of 0.0200 mol-L 1 cyclohexane and 0.100 mol-I. 1 methylcyclopentane is prepared. Is the system at equilibrium If not, will it will form more reactants or more products (b) What are the concentrations of cyclohexane and methylcyclohexane at equilibrium (c) If the temperature is raised to 50.°C, the concentration of cyclohexane becomes 0.100 mol-L 1 when equilibrium is reestablished. Calculate the new equilibrium constant, (d) Is the reaction exothermic or endothermic at 25°C Explain your conclusion. 

To deduce the relation between rate constants and equilibrium constants, we note that the equilibrium constant for a chemical reaction in solution that has the form A + B C + D is... 

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