Chemical equilibrium A dynamic reaction

Chemical equilibrium A dynamic reaction system in which the concentrations of all reactants and products remain constant as a function of time. 

Chemical change the change of substances into other substances through a reorganization of the atoms a chemical reaction. (1.9) Chemical equation a representation of a chemical reaction showing the relative numbers of reactant and product molecules. (3.8) Chemical equilibrium a dynamic reaction system in which the concentrations of all reactants and products remain constant as a function of time. (13)... 

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. 

Chemical equilibrium A dynamic state The concentrations of the reactants and products remain constant because the rate at which the forward reaction occurs is the same as that of the back reaction. 

Chemical equilibrium A dynamic state in which the rates of forward and reverse reactions are identical a system in equilibrium will not spontaneously depart from this condition. Chemiluminescence The emission of energy as electromagnetic radiation during a chemical reaction. 

There is a lot of evidence that chemical equilibrium is dynamic. One example of this evidence is relevant to the ammonia equilibrium. Imagine carrying out two ammonia syntheses with the same starting conditions, but using D2 (deuterium) in place of H2 in one of them (Fig. 9.2). The two reaction mixtures reach equilibrium with almost exactly the same composition, except that D2 and ND3 are present in one of the systems instead of H2 and NH3. Suppose we now combine the two mixtures and... 

Using the transformed variables the reactive problem (Eq. (5)) is completely equivalent to a nonreactive problem (Eq. (4)) of reduced dimension. Hence, in the limit of chemical equilibrium the dynamic behavior of reaction separation processes is equivalent to the dynamic behavior of nonreactive processes. 

Chemical equilibrium is the state reached by a reaction mixture when the rates of forward and reverse reactions have become equal. If you observe the reaction mixture, you see no net change, although the forward and reverse reactions are continuing. The continuing forward and reverse reactions make the equilibrium a dynamic process. 

For the ideal chemical cases, a dynamic model is simulated in Matlab. This model consists of ordinary differential equations for tray compositions and algebraic equations for vapor-liquid equilibrium, reaction kinetics, tray hydraulics, and tray energy balances. The dynamic model is used for steady-state design calculations by mnning the simulation out in time until a steady state is achieved. This dynamic relaxation method is quite effective in providing steady-state solutions, and convergence is seldom an issue. 

Stratospheric ozone is in a dynamic equilibrium with a balance between the chemical processes of formation and destruchon. The primary components in this balance are ultraviolet (UV) solar radiation, oxygen molecules (O2), and oxygen atoms (O) and may be represented by the following reactions ... 

Chemists picture equilibrium as a dynamic balance between opposing reactions. An understanding of the Law of Chemical Equilibrium can be built upon this basis. 

Another difficulty is that spontaneous chemical reactions do not go to completion. Even if a spontaneous reaction is exothermic, it proceeds only till it reaches equilibrium. But in our golf ball analogy, equilibrium is reached when all of the golf balls are on the lower level. Oui analogy would lead us to expect that an exothermic reaction would proceed until all of the reactants are converted to products, not to a dynamic equilibrium. 

It is found that after the elapse of a sufficient time interval, all reversible reactions reach a state of chemical equilibrium. In this state the composition of the equilibrium mixture remains constant, provided that the temperature (and for some gaseous reactions, the pressure also) remains constant. Furthermore, provided that the conditions (temperature and pressure) are maintained constant, the same state of equilibrium may be obtained from either direction of a given reversible reaction. In the equilibrium state, the two opposing reactions are taking place at the same rate so that the system is in a state of dynamic equilibrium. 

Why Do We Need to Know This Material The dynamic equilibrium toward which every chemical reaction tends is such an important aspect of the study of chemistry that four chapters of this book deal with it. We need to know the composition of a reaction mixture at equilibrium because it tells us how much product we can expect. To control the yield of a reaction, we need to understand the thermodynamic basis of equilibrium and how the position of equilibrium is affected by conditions such as temperature and pressure. The response of equilibria to changes in conditions has considerable economic and biological significance the regulation of chemical equilibrium affects the yields of products in industrial processes, and living cells struggle to avoid sinking into equilibrium. 

Like physical equilibria, all chemical equilibria are dynamic equilibria, with the forward and reverse reactions occurring at the same rate. In Chapter 8, we considered several physical processes, including vaporizing and dissolving, that reach dynamic equilibrium. This chapter shows how to apply the same ideas to chemical changes. It also shows how to use thermodynamics to describe equilibria quantitatively, which puts enormous power into our hands—the power to control the And, we might add, to change the direction of a reaction and the yield of products,... 

Like phase changes, chemical reactions tend toward a dynamic equilibrium in which, although there is no net change, the forward and reverse reactions are still taking place, but at matching rates. What actually happens when the formation of ammonia appears to stop is that the rate of the reverse reaction,... 

A catalyst speeds up both the forward and the reverse reactions by the same amount. Therefore, the dynamic equilibrium is unaffected. The thermodynamic justification of this observation is based on the fact that the equilibrium constant depends only on the temperature and the value of AGr°. A standard Gibbs free energy of reaction depends only on the identities of the reactants and products and is independent of the rate of the reaction or the presence of any substances that do not appear in the overall chemical equation for the reaction. 

Like all chemical equilibria, this equilibrium is dynamic and we should think of protons as ceaselessly exchanging between HCN and H20 molecules, with a constant but low concentration of CN and H30+ ions. The proton transfer reaction of a strong acid, such as HCl, in water is also dynamic, but the equilibrium lies so strongly in favor of products that we represent it just by its forward reaction with a single arrow. 

Chemical reactions that are reversible are said to be in dynamic equilibrium because opposite reactions take place simultaneously at the same rate. A system that is at equilibrium can be shifted toward either reactants or products if the system is subjected to a stress. Changes in concentration, temperature, or pressure are examples of stresses. 

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