Equilibrium changes affecting

For the liquid-phase mass-transfer coefficient /cl, the effects of total system pressure can be ignored for all practical purposes. Thus, when using Kq and /cl for the design of gas absorbers or strippers, the primary pressure effects to consider will be those which affect the equilibrium curves and the values of m. If the pressure changes affect the hydrodynamics, then Icq, and a can all change significantly. 

What conditions might alter the equilibrium state Concentration and temperature These are factors that affect the rate of reaction. Equilibrium is attained when the rates of opposing reactions become equal. Any condition that changes the rate of one of the reactions involved in the equilibrium may affect the conditions at equilibrium. 

We are not satisfied with the conclusion that this change or that change affects the equilibrium concentrations. We would also like to predict the direction of the effect (does it favor products or reactants ) and the magnitude of the effect (how much does it favor products or reactants ). The first desire, to know the qualitative effects, is answered by a generalization first proposed by a French chemist, Henry Louis Le Chatelier, and now called Le Chatelier s Principle. 

A merocyanine dye, l-ethyl-4-(2-(4-hydroxyphenyl)ethenyl)pyridinium bromide (M-Mc, 2), exhibits a large spectral change according to the acid-base equilibrium [40, 41]. The equilibrium is affected by the local electrostatic potential and the polarity of the microenvironment around the dye. Hence, this dye is useful as a sensitive optical probe for the interfacial potential and polarity when it is covalently attached to the polyelectrolyte backbone. 

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. 

The equilibrium constant Ka is independent of pressure for those cases where the standard states are taken as the pure components at 1 atm. This case is the one used as the basis for deriving equation 2.6.9. Tjie effect of pressure changes then appears in the terms KfjP and ps + t+ b c . The influence of pressure on KfjP is quite small. However, for cases where there is no change in the total number of gaseous moles during the reaction, this is the only term by which pressure changes affect the equilibrium yield. For these... 

Under what circumstances is the position of equilibrium not affected by a change in the pressure on the system Give examples, and explain your answer. 

How a chemical system at equilibrium changes when conditions change was first stated by Henri Louis Le Chatelier (1850-1936) in 1884. Le Chatelier was a professor at a mining school in France who worked on both the theoretical and practical aspects of chemistry. His research on the chemistry of cements led him to formulate a principle to predict how changing the pressure affected a chemical system. In the publication Annals of Mines in 1888, Le Chatelier stated the principle that bears his name Every change of one of the factors... 

Note that the variable Y must be able to affect the position of equilibrium change of the partial pressure of an reactive species (e.g., inert He gas) cannot affect , and therefore cannot result in any re-equilibration change in the system. In all cases, the rigorous thermodynamic formulation (8.43) may be used to guide qualitative applications of the Le Chatelier concept. 

For each reaction, tell the effect on Ke and on the equilibrium position of each change listed in the table. Assume that each change affects the reaction mixture only after it has already once reached equilibrium. Use the following symbols in complet-... 

The composition of an equilibrium mixture can be altered by changes in concentration, pressure (volume), or temperature. The qualitative effect of these changes is predicted by Le Chatelier s principle, which says that if a stress is applied to a reaction mixture at equilibrium, net reaction occurs in the direction that relieves the stress. Temperature changes affect equilibrium concentrations because Kc is temperature-dependent. As the temperature increases, Kc for an exothermic reaction decreases, and Kc for an endothermic reaction increases. 

Which of these changes affect the composition of the equilibrium mixture, but leave the value of the equilibrium constant Kc unchanged Which of the changes affect the value of fCc Which affect neither the composition of the equilibrium mixture nor Kc ... 

We have seen how Le Chatelier s principle can be used to predict the effect of several types of changes on a system at equilibrium. As a summary of these ideas, Table 6.4 shows how various changes affect the equilibrium position of the endothermic reaction... 

A spectrophotometric study (544) of the competition of 1-dodecene with a series or 3- or 4-substituted styrenes in these complexes has shown that the equilibrium is affected not only by changing the substituents on styrene but to an even greater extent by change of Z. 

Temperature changes affect not only systems at equilibrium but also the value of equilibrium constants. In fact, equilibrium constants changing with temperature is the reason that equilibria change with temperature. For example, consider Kgq for the ammonia synthesis equilibrium. 

Temperature changes affect the values of equilibrium constants. 

When does a pressure change affect a chemical equilibrium ... 

The nucleophilic addition of water to a ketone or aldehyde is slow in pure water but is catalyzed by both acid and base. Like all catalysts, acids and bases don t change the position of the equilibrium they affect only the rate at which the hydration reaction occurs. 

In 1888, the French chemist Henri-Louis Le ChStelier discovered that there are ways to control equilibria to make reactions, including this one, more productive. He proposed what is now called Le Chatelier s principle If a stress is applied to a system at equilibrium, the system shifts in the direction that relieves the stress. A stress is any kind of change in a system at equilibrium that upsets the equilibrium. You can use Le Chatelier s principle to predict how changes in concentration, volume (pressure), and temperature affect equilibrium. Changes in volume and pressure are interrelated because decreasing the volume of a reaction vessel at constant temperature increases the pressure inside. Conversely, increasing the volume decreases the pressure. 

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