Effect of a Change in Temperature on Equilibrium

For an exothermic reaction, heat flows out of the system. We might say that this heat is a product of the reaction. We can note this explicitly in a form of a thermochemical equation  

Once we do this, the situation begins to resemble our discussion of the addition or removal of a product from the reaction mixture. When temperature is increased, we stress the equilibrium by adding heat. According to LeChatelier s principle, the system will respond to offset the stress and absorb the excess heat, moving the equilibrium toward reactants. On the other hand, when the temperature is lowered, heat flows out from the system, and the system will respond by generating additional heat—moving toward products. 

Adding the word heat to an equation helps us see which direction the reaction will shift. But it should not imply that heat is a quantity that a substance can possess. 

Using similar reasoning, if the temperature is increased, the endothermic system will move in the direction that absorbs heat—toward the products. If the temperature is decreased, a shift toward reactants liberates heat to offset this stress. We summarize the possible responses of chemical reactions to temperature changes in Table 12.3. 

Unlike changes in the concentrations of reactants or products, in which the equilibrium constant is unaffected, a temperature shift also changes the vahie of the equilibrium constant. (As for rate constants, we are again confronted with a constant that varies as a function of temperature ) The fact that equilibrium constants vary with temperature, however, is important in the way chemical reactions occur in industrial processes. Often, high temperatures are required for 

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When Cases Are Present Effect of a Change in Temperature on Equilibrium Effect of a Catalyst on Equilibrium... 

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