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Im thinking specifically of N2 + 3 H2 ⇌ 2 NH3. Its an exothermic reaction, therefore heat is generated. Im trying to understand how Chateliers principle interacts with this reaction. I understand that if you remove heat, Chateliers principle dictates that the equilibrium shifts to the product-side. I cant quite understand why though, do the reactants kind of know how warm it is and then decide, if its too warm "No, its too warm, lets not react and make it too warm"?

A followup on that question too, these reactions happen in enclosed places where temperature and pressure can be manipulated.Is it just efficiency of these containers that prevent the containers to not get as hot as the sun? If temperature wasnt manipulated, would the temperature keep rising?

marked as duplicate by a-cyclohexane-molecule, A.K., Todd Minehardt, Zhe, Satwik Pasani Aug 10 at 16:14

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  • For your second set of questions: you only have a finite amount of reactants, and hence can only generate a finite amount of heat, so the temperature would only rise until the reaction has proceeded to equilibrium. – a-cyclohexane-molecule Aug 10 at 11:16

Unlike the other factors affecting chemical equilibrium, (namely concentration, pressure), temperature follows the Le Chatelier principle via a different mechanism.

Temperature alters the equilibrium constant $K$, and this change in $K$ also changes the relative concentrations of the reactants and the products. The way in which the equilibrium constant depends on temperature is given by Van't Hoff equation: $$\frac{d \ln K}{d T}=\frac{\Delta H}{RT^2}$$ Therefore, for exothermic reactions, the change in $K$ acts as if heat is one of the products, since increasing the temperature causes the $K$ to decrease, making the equilibrium at lower temperatures more favorable for Haber's process for making ammonia. (While this only talks of the equilibrium concentrations, lower temperatures in general result in slower rates, hence a balance is always sought)

While for your other question, as the temperature increases, the equilibrium is reached faster by both increasing ammonia (the cause of the increasing temperatures) and the decreasing $K$, until at a certain temperature, the reaction reaches equilibrium. I am not sure of the practical constraints employed in temperature regulation in the industry.

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