Paranoid_Glitch
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For dynamic equilibrium (suppose the forward reaction is exothermic) if i were to increase the temperature of the equilibrium why would the endothermic reaction be favored, isn't heat energy being absorbed, hence increasing the temperature of the system?
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jessedoell
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In a dynamic equilibrium, the principle is that the equilibrium will shift to OPPOSE the change on the system. So like you say if the forward reaction is exothermic, and you increase temperature, then the equilibrium is going to shift to oppose the change; by making it colder. To do this, it shifts in the endothermic- and in this case backwards- direction.
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Paranoid_Glitch
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(Original post by jessedoell)
In a dynamic equilibrium, the principle is that the equilibrium will shift to OPPOSE the change on the system. So like you say if the forward reaction is exothermic, and you increase temperature, then the equilibrium is going to shift to oppose the change; by making it colder. To do this, it shifts in the endothermic- and in this case backwards- direction.
Yeah Le Chatelier's Principle. Though if it absorbs heat shouldn't that increase the temperature of the equilibrium mixture. My misconception might be drawn from the idea that i do not actually understand the definition of exothermic and endothermic reactions. Could you help define them?
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jessedoell
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An exothermic reaction is one where more energy is given out than taken in, so it will have a negative enthalpy value. For example, the enthalpy of combustion of ethanol is -1058kJmol-1. This results in a net increase in temperature of the reaction.
An endothermic reaction is where more energy is taken in than given out, so it will have a positive enthalpy value. The enthalpy of solution of ammonium nitrate is, +25.7kJmol-1. This results in a net decrease in temperature of the system.

If you add extra heat to the system, the equilibrium will shift in endothermic direction, which will cool down the system, opposing the heat being added to the system. It works visa versa.
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Paranoid_Glitch
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(Original post by jessedoell)
An exothermic reaction is one where more energy is given out than taken in, so it will have a negative enthalpy value. For example, the enthalpy of combustion of ethanol is -1058kJmol-1. This results in a net increase in temperature of the reaction.
An endothermic reaction is where more energy is taken in than given out, so it will have a positive enthalpy value. The enthalpy of solution of ammonium nitrate is, +25.7kJmol-1. This results in a net decrease in temperature of the system.

If you add extra heat to the system, the equilibrium will shift in endothermic direction, which will cool down the system, opposing the heat being added to the system. It works visa versa.
Why is it negative are we subtracting the enthaply value of the products from the reactants?
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jessedoell
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(Original post by Paranoid_Glitch)
Why is it negative are we subtracting the enthaply value of the products from the reactants?
For enthalpy changes, you can calculate via using:
Energy of Bonds Broken - Energy of Bonds formed

Breaking bonds takes in energy, forming bonds releases energy.
So releasing more energy than taking in results in a negative value. This is why temp increases, heat is given out. The opposite for endothermic
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Paranoid_Glitch
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(Original post by jessedoell)
For enthalpy changes, you can calculate via using:
Energy of Bonds Broken - Energy of Bonds formed

Breaking bonds takes in energy, forming bonds releases energy.
So releasing more energy than taking in results in a negative value. This is why temp increases, heat is given out. The opposite for endothermic
Oh okay, thank you
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