Principle of LeChatelier

The effect of pressure will be greatest when the area occupied by the products of reaction is most different from that of the reactants. If the products occupy less area, the principle of LeChatelier shows that reaction will proceed further to completion if the products are more bulky than the reactants the surface pressure will reduce the extent of reaction. 

These observations and others on the direction of the shift in equilibrium in response to a given change are usually summarized by a statement referred to as the Principle of LeChatelier and Braun (but also known as the Principle of Moderation or the Principle of Spite ) ... 

Equations (11.70) and (11.71) are quantitative statements of the principle of LeChatelier They describe the dependence of the advancement of the reaction at equilibrium on temperature and on pressure. Since G" is positive, the sign oiid JdT) depends on the sign of AH. If AH is +, an endothermic reaction, then (diJdT)p is +, and an increase in temperature increases the advancement at equilibrium. For an exothermic reaction, AH is —, so d JdT) is — increase in temperature will decrease the equilibrium advancement of the reaction. 

We may state the principle of LeChatelier in the following way. If the external constraints under which an equilibrium is established are changed, the equilibrium will shift in such a way as to moderate the effect of the change. 

In the presence of n-butane, Ky becomes smaller than in the ternary system because of the increasing activity coefficient of methanol in the presence of butane, which leads to an increase of Kx and the equilibrium conversion. But this effect is compensated by the dilution of the reaction mixture, which leads to a decrease of the equilibrium conversion following the principle of LeChatelier, since for the reaction considered Eu, is negative. 

Why is the presence of coesite or stishovite near a crater taken as evidence that the crater was formed by impact of a meteorite In what way is the principle of LeChatelier involved in your answer ... 

Such hydrophobic H-bonding naturally leads to an appreciable reduction in volume, and is therefore increasingly favored at higher pressures. Similarly, in the spirit of LeChatelier s principle, one may expect that the presence of a hydrophobic solute promotes formation of cage structures, i.e., tends to shift the cluster... 

In this chapter, the diverse coupling constants and MEC components identified in the combined electronic-nuclear approach to equilibrium states in molecules and reactants are explored. The reactivity implications of these derivative descriptors of the interaction between the electronic and geometric aspects of the molecular structure will be commented upon within both the EP and EF perspectives. We begin this analysis with a brief survey of the basic concepts and relations of the generalized compliant description of molecular systems, which simultaneously involves the electronic and nuclear degrees-of-freedom. Illustrative numerical data of these derivative properties for selected polyatomic molecules, taken from the recent computational analysis (Nalewajski et al., 2008), will also be discussed from the point of view of their possible applications as reactivity criteria and interpreted as manifestations of the LeChatelier-Braun principle of thermodynamics (Callen, 1962). 

The reactor can operate with either a liquid-phase reaction or a gas-phase reaction. In both types, temperature is very important. With a gas-phase reaction, the operating pressure is also a critical design variable because the kinetic reaction rates in most gas-phase reactions depend on partial pressures of reactants and products. For example, in ammonia synthesis (N2 + 3H2 O 2NH3), the gas-phase reactor is operated at high pressure because of LeChatelier s principle, namely that reactions with a net decrease in moles should be mn at high pressure. The same principle leads to the conclusion that the steam-methane reforming reaction to form synthesis gas (CH4 + H20 O CO + 3 H2) should be conducted at low pressure. 

By application of LeChatelier s principle, one can see that reaction 10.5 is favored at lower pH. The reaction of NH2CI with NOM can be interpreted as chloramine demand exerted by NOM oxidation, and written as follows ... 

The overall, generally small, effect of pressure to increase H bond formation can be understood as a molar volume change. It is another fulfillment of LeChatelier s principle—H bonds reduce the space occupied by the molecules so their formation is enhanced by a process... 

The operation of a buffer solution depends on the common ion effect, a special case of LeChatelier s Principle. 

Human behavior often follows LeChatelier s principle. Provide one example and explain in terms of LeChatelier s principle. 

This is an example of LeChatelier s principle, because the loss of H3O+ (the stress) is compensated by the dissociation of acetic acid to produce more H3O+. 

When strong bases are added to a carboxylic acid, neutralization occurs. The acid protons are removed by the OH to form water and the carboxylate ion. The equilibrium shown in the reaction above is shifted to the right, owing to removal of H+. This is an illustration of LeChatelier s principle. 

The answer is C. In the experiment, the hydrogen is removed. Such a change in concentration will upset the equilibrium. We have to approach this problem in terms of LeChatelier s principle. Changes in the concentrations of reactants or products of this reaction will turn the system into a non-equilibrium state. The result will be an adjustment of the reaction mode to restore the system to equilibrium. So if we take away, the backward reaction will be favored for restoring the equilibrium. 

Use an internet search engine to locate information on LeChatelier. State his principle in simple terms. Give an example of LeChatelier s Principle being appUed to a nonchemical equiUbrium. 

Recall from Section 19-1 that the common ion effect is a special case of LeChatelier s Principle. Thus, the common ion effect applies to solubility equilibria just as it does to other ionic equilibria. Silver acetate, AgCH3COO, is a slightly soluble salt... 

Concepts presented in this and the two preceding chapters give students an integrated insight into some central issues in chemistry Why and in which direction does the reaction proceed How fast does it proceed and How far does it proceed The critical use of the equilibrium constant summarizes these critical interpretations. Important concepts in prior chapters are utilized to aid student use of LeChatelier s Principle— predicting and calculating the effects on reaction direction and extent when temperature, pressures, concentrations, and other reaction conditions are altered. 

The plot is shown on Figure E20.1. By following any of the four curves from low to high tenperature, it is observed that the equilibrium conversion decreases with increasing tenperature at constant pressure. This is a consequence of LeChatelier s principle, because the methanol formation reaction is exothermic. By following a vertical line from low to high pressure, it is observed that the equilibrium conversion increases with increasing pressure at constant tenperature. This is also a consequence of LeChatelier s principle. 

LeChatelier s principle states that if a system at equilibrium is subjected to a stress, the equilibrium will shift in a direction that will relieve the stress. One such stress is a change of concentration. In this activity, you will see how changing the concentration of a reactant or product creates a new equilibrium. 

Does this agree with LeChatelier s Principle that for an exothermic reaction the system will shift to form more reactants at higher temperatures Yes, it does. Recall, that that only temperature will affect the value of the equilibrium constant. More reactants are formed because the value of the equilibrium constant decreased when the temperature increased. 

To make MnS(s) more soluble, the above equilibrium must be shifted to the right. Applying LeChatelier s Principle, any process which will reduce either [Mn2+] or [S2 ] will do this. In the presence of 0.10 M HC1 (a strong acid), competing equilibria will lower [S2 ] by producing the weak acids, HS and H2S ... 

The best biography is available at the French Website http //www.annales.com/ archives/xAc.html. The short article Man of principle by Michael Sutton in Chemistry in Britain, June 2000, 43, also includes a nice introduction to the man and the background to his science. Websites bearing the same title as Sutton s article proliferate two of the better ones (which include photographs) are http //www.woodrow.org/ teachers/ci/1992/LeChatelier.html and http //www.stormpages.com/aboutchemists/ lechatelier.html. 

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