Le Chatelier’s principle When a stress

Le Chatelier s principle When a stress is applied to a system in dynamic equilibrium, the equilibrium tends to adjust to minimize the effect of the stress. 

Le Chatelier s principle When a stress is applied to a system in dynamic equilibrium, the equilibrium adjusts to minimize the effect of the stress. Example a reaction at equilibrium tends to proceed in the endothermic direction when the temperature is raised, leveling The observation that strong acids all have the same strength in water, and all behave as though they were solutions of H,Of ions. 

Le Chatelier s Principle When a stress or change in conditions is applied to a system at equilibrium, the point of equilibrium will shift in such a manner as to relieve the applied stress. 

According to Le Chatelier s principle, when a stress (a change in concentration, pressure, or temperature) is applied to a system at equilibrium, the equilibrium is shifted in the direction that relieves the stress. 

Le Chatelier s principle When a stress is placed on a system atequi-hbrium, the system shifts to relieve that stress, neutral The term that describes a solution with equal concentrations 0fH3O+andOH . 

Le Chatelier s principle provides a means for predicting how systems at equilibrium respond to a change in conditions. When a stress is applied to an equilibrium by adding a reactant or product, by adding a reagent that reacts with one of the reactants or products, or by changing the volume, the system responds by moving in the direction that relieves the stress. 

Le Chatelier s principle when stressed, a system that was at equilibrium returns to its equilibrium state by reacting in a manner that relieves the stress, (p. 148)... 

Le Chatelier s principle is a powerful tool for explaining how a reaction at equilibrium shifts when a stress is placed on the system. In this experiment, you can use Le Chatelier s principle to evaluate the relative solubilities of two precipitates. By observing the formation of two precipitates in the same system, you can infer the relationship between the solubilities of the two ionic compounds and the numerical values of their solubility product constants (K ). You will be able to verify your own experimental results by calculating the molar solubilities of the two compounds using the Ksp for each compound. 

The qualitative reasoning expressed in Le Chatelier s principle is a helpful guide a system at equilibrium adjusts so as to minimize any stress applied to it. For hydration-dehydration equilibria, the key stress factor is the water concentration. Adding water to a hydration-dehydration equilibrium mixture causes the system to respond by consuming water. More alkene is converted to alcohol, and the position of equilibrium shifts to the right. When we prepare an alcohol from an alkene, we use a reaction medium in which the molar concentration of water is high—dilute sulfuric acid, for example. 

The response of a gas-phase equilibrium to pressure changes is an example of Le Chatelier s principle, where the stress is the change in pressure. When the pressure of a reaction mixture at equiUbrium is increased, the system will respond by shifting the equilibrium in a direction that decreases the pressure, that is, in the direction that reduces the number of gas-phase molecules in the reaction mixture. 

FIGURE 11.6 An illustration of Le Chatelier s principle when an applied stress favors the products, in this situation, there is a momentary surge from ieft to right before equilibrium is reestablished at the new position. At this new position, the amount of product is greater than it was and the amount of reactant is less. 

According to Le Chatelier s principle, when stress is applied to a reaction at equilibrium,... 

Another crystallization technique is used when the isolation of a highly water-soluble compound in its salt form is required from aqueous reaction mixtures. This technique takes advantage of the common-ion effect and is based on the le Chatelier s principle, which states that, if, to a system in equilibrium, a stress is applied, the system will react so as to relieve the stress. Thus, in aqueous solutions, the solubility of the compound in salt form can be reduced by adding large amoimts of a common ion which is more soluble than the salt of the compoimd. 

Apply Le Chatelier s principle to determine whether the forward or reverse reaction is favored when a stress such as concentration, temperature, or pressure is applied to an equilibrium system. 

Chemical and mechanical equilibria are similar in that both respond to stresses by adjusting until new equilibria are reached. Henri Le Chatelier, the chemist pictured in Figure 9, studied the way in which chemical equilibria respond to changes. His findings are known as Le Chatelier s principle. This principle states that when a system at equilibrium is disturbed, the system adjusts in a way to reduce the change. Some situations in our lives are analogies for Le Chatelier s principle. For example, if you are disturbed by a loud noise, you may move to a quieter location. 

When predicting the results of a stress on an equilibrium using Le Chatelier s principle, it is important to have the equation for the reaction in... 

Le Chatelier s principle applies to these equilibria, as it does to all equilibria. One way to exert a stress on a solubility equilibrium is to change the amount of solvent. Adding solvent reduces the concentration of dissolved substance more solid then tends to dissolve to restore the concentration of the dissolved substance to its equilibrium value. If an excess of solvent is added so that all of the solid dissolves, then obviously the solubility equilibrium ceases to exist and the solution is unsaturated. In a vaporization-condensation equilibrium, this corresponds to the complete evaporation of the condensed phase. Removing solvent from an already saturated solution forces additional solid to precipitate in order to maintain a constant concentration. A volatile solvent is often removed by simply letting a solution stand uncovered until the solvent evaporates. When conditions are right, the solid forms as crystals on the bottom and sides of the container (Fig. 16.1). 

There is a general rule called Le Chatelier s principle that can often be applied to systems at equilibrium. Le Chatelier s principle states that when a system at equilibrium is stressed, the system will shift in a direction that will reduce that stress. 

There is a general rule that helps us to predict the direction in which an equilibrium reaction will move when a change in concentration, pressure, volume, or temperature occurs. The rule, known as Le Chatelier s principle, states that if an external stress is applied to a system at equilibrium, the system adjusts in such a way that the stress is partially offset. The word stress here means a change in concentration, pressure, volume, or temperature that removes a system from the equilibrium state. We will use Le Chatelier s principle to assess the effects of such changes. 

The equilibrium concentrations of reactants and products can be altered by applying stress to the system, for example, by changing the temperature, the pressure, or the concentration of one of the reactants. The effects of such changes can be predicted from Le Chatelier s principle, which states that when stress is applied to a system at chemical equilibrium, the equilibrium will shift in a direction that tends to relieve or counteract that stress. The effects of temperature, pressure, and concentrations on chemical equilibria are considered below. 

Adding an acid When an acid is added to this buffered solution, as shown in Figure 18.27b, the equilibrium shifts to the left. According to Le Chatelier s principle, the added H+ ions from the acid are a stress on the equilibrium, which is relieved by their reaction with F ions to form additional undissociated HF molecules. 

Strategy (a) Determine the stress that is applied to the system, and then apply Le Chatelier s principle to determine the direction in which the equihbrimn will respond, (b) At the instant when some NH3 is added, the system is no longer at equilibrium. Calculate for the reaction at this point, and compare its value to to determine the direction of the net reaction to reach equihbrium. 

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