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The equilibrium constant of a chemical reaction is the value of its reaction quotient at chemical equilibrium, a state approached by a dynamic chemical system after sufficient time has elapsed at which its composition has no measurable tendency towards further change. For a given set of reaction conditions, the equilibrium constant is ...
where ln denotes the natural logarithm, is the thermodynamic equilibrium constant, and R is the ideal gas constant.This equation is exact at any one temperature and all pressures, derived from the requirement that the Gibbs free energy of reaction be stationary in a state of chemical equilibrium.
The value of the equilibrium constant for the formation of a 1:1 complex, such as a host-guest species, may be calculated with a dedicated spreadsheet application, Bindfit: [4] In this case step 2 can be performed with a non-iterative procedure and the pre-programmed routine Solver can be used for step 3.
The Hammett equation predicts the equilibrium constant or reaction rate of a reaction from a substituent constant and a reaction type constant. The Edwards equation relates the nucleophilic power to polarisability and basicity. The Marcus equation is an example of a quadratic free-energy relationship (QFER). [citation needed]
The fourth row, labeled E, is the sum of the first two rows and shows the final concentrations of each species at equilibrium. It can be seen from the table that, at equilibrium, [H +] = x. To find x, the acid dissociation constant (that is, the equilibrium constant for acid-base dissociation) must be specified.
The reaction quotient plays a crucial role in understanding the direction and extent of a chemical reaction's progress towards equilibrium: Equilibrium condition: At equilibrium, the reaction quotient (Q) is equal to the equilibrium constant (K) for the reaction. This condition is represented as Q = K, indicating that the forward and reverse ...
The relation between the Gibbs free energy and the equilibrium constant can be found by considering chemical potentials. [ 1 ] At constant temperature and pressure in the absence of an applied voltage, the Gibbs free energy , G , for the reaction depends only on the extent of reaction : ξ (Greek letter xi ), and can only decrease according to ...
which relates the Gibbs energy to a chemical equilibrium constant, the van 't Hoff equation can be derived. [ 9 ] Since the change in a system's Gibbs energy is equal to the maximum amount of non-expansion work that the system can do in a process, the Gibbs-Helmholtz equation may be used to estimate how much non-expansion work can be done by a ...