Using Le Chatelier's Principle with a change of temperature
Students, remember that in discussing the reaction rate, temperature is also one of the factors which affect the reaction rate.
If we think about changing temperature, so we have to look at the dynamic equilibrium, check the forward reaction, endotermic or exotermic.
If the forward reaction is endotermic, the sign of enthalpy change is positive. If the temperature is increased, what will happen? The endotermic reaction is a reaction which the reactants absorb the heat. So the kinetic energy of the reactants will increase and the number of efective collision will increase. Because of this, the reaction rate of the forward reaction is greater than the reverse reaction, so that the equilibrium will shift to the right and the concentration of products increase. The equilibrium constant is greater than the initial.
For another equilibrium, if the forward reaction is exothermic, the sign of enthalpy change is negative. The reverse reaction is endothermic and the sign of enthalpy is positive. If the temperature is increased, the products will absorb the energy and their kinetic energy will increase. The reaction rate of the reverse reaction is greater than the forward reaction. So the equilibrium will shift to the endotermic reaction, so it will shift to the left and the concentration of reactants increase; the equilibrium constant is smaller than before.
Why does the endothermic reaction absorb the energy when we increase the temperature?
According to Le Chatelier, the position of equilibrium will shift to counteract the change. This means that the position of equilibrium will shift so that the temperature is reduced again. (Action and reaction)
If the temperature of an equilibrium system is 200°C, and we increase the temperature to 300°C, what will happen? How can the reaction counteract the change we have made? What the reaction of this action? The reaction is there is a cooling down, to make the temperature reduces. The reactants will absorb the energy (heat) that we put in, so the equilibrium shift to the endothermic reaction.
Students, remember that in discussing the reaction rate, temperature is also one of the factors which affect the reaction rate.
If we think about changing temperature, so we have to look at the dynamic equilibrium, check the forward reaction, endotermic or exotermic.
If the forward reaction is endotermic, the sign of enthalpy change is positive. If the temperature is increased, what will happen? The endotermic reaction is a reaction which the reactants absorb the heat. So the kinetic energy of the reactants will increase and the number of efective collision will increase. Because of this, the reaction rate of the forward reaction is greater than the reverse reaction, so that the equilibrium will shift to the right and the concentration of products increase. The equilibrium constant is greater than the initial.
For another equilibrium, if the forward reaction is exothermic, the sign of enthalpy change is negative. The reverse reaction is endothermic and the sign of enthalpy is positive. If the temperature is increased, the products will absorb the energy and their kinetic energy will increase. The reaction rate of the reverse reaction is greater than the forward reaction. So the equilibrium will shift to the endotermic reaction, so it will shift to the left and the concentration of reactants increase; the equilibrium constant is smaller than before.
Why does the endothermic reaction absorb the energy when we increase the temperature?
According to Le Chatelier, the position of equilibrium will shift to counteract the change. This means that the position of equilibrium will shift so that the temperature is reduced again. (Action and reaction)
If the temperature of an equilibrium system is 200°C, and we increase the temperature to 300°C, what will happen? How can the reaction counteract the change we have made? What the reaction of this action? The reaction is there is a cooling down, to make the temperature reduces. The reactants will absorb the energy (heat) that we put in, so the equilibrium shift to the endothermic reaction.
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