Exothermic vs Endothermic
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Exothermic vs Endothermic
How can we tell if a reaction is exothermic or endothermic? I know that an exothermic reaction releases heat and that an endothermic reaction requires heat, but how exactly can we figure this out when looking at a reaction equation?
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Re: Exothermic vs Endothermic
The reaction equation will tell us if there is heat being lost or gained either through the words of the problem or you might see like a triangle on top of the arrows or on either sides of the equation. The triangle just means that heat is being used or that there is heat in general.
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Re: Exothermic vs Endothermic
For most questions, they will give the change in enthalpy, and a negative enthalpy means an exothermic reaction.
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Re: Exothermic vs Endothermic
It might be helpful to note that all combustion and neutralization reactions are exothermic and usually decomposition reactions are endothermic as it involves the breaking of bonds. Other than that, if the delta H of the reaction is given on the side of the equation, we can tell whether the reaction is exothermic or endothermic by looking at the sign of delta H (if it's negative, the reaction is exothermic whereas if it is positive it is endothermic).
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Re: Exothermic vs Endothermic
In general, if the reaction enthalpy is given, then we should know whether the reaction is exo- or endo- thermic. Negative values of delta H mean heat is released and the reaction is exothermic while positive values of delta H mean that heat is absorbed and the reaction is endothermic.
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Re: Exothermic vs Endothermic
If the enthalpy value lies on the reactants side, the reaction is endothermic. If the enthalpy value lies on the products side, the reaction is exothermic.
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Re: Exothermic vs Endothermic
A question will usually have it as a given whether or not the reaction is releasing or absorbing heat. This is indicated with a +deltaH or -deltaH
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Re: Exothermic vs Endothermic
Negative delta H means an exothermic reaction while positive delta H means an endothermic reaction. This is because energy is released in an exothermic reaction as the substance/compound goes to a lower energy state and vice versa for an endothermic reaction.
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Re: Exothermic vs Endothermic
You can figure this out with the delta H value given. If it is negative, it is exothermic since it is releasing and if it is positive, it is endothermic. Hope this helps!
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Re: Exothermic vs Endothermic
if given the change in heat, you can look at that to determine if the reaction is endothermic or exothermic. For it to be exothermic it would be negative because heat is being released while for endothermic it'd be positive because heat and energy are inputs.
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Re: Exothermic vs Endothermic
There are many ways to find if a reaction will be exo or endo thermic. Sometimes the problem will give you a value for delta H, and if it is negative, it will be exothermic, and if positive, will be endothermic. Also, you might be given other information that you are supposed to use to calculate whether something is endo or exo thermic.
Re: Exothermic vs Endothermic
If the change of enthalpy given (delta H) is positive, the reaction is exothermic and vice versa. In general though, if you don't have delta H given, there are clues like the type of the reaction (combustion reactions are exothermic and decomposition reactions are usually endothermic).
Re: Exothermic vs Endothermic
So far, the questions have given us delta H. If delta H is negative, the reaction is exothermic and if delta H is positive, the reaction is endothermic.
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Re: Exothermic vs Endothermic
If you look at the change in enthalpy for a reaction, then that is one way you can tell if it is exothermic or endothermic. Exothermic reactions have negative enthalpies because they release heat. Endothermic reactions have positive enthalpies because they require heat. You can also determine whether the reaction is exothermic or endothermic based on the type of reaction that is occurring. For example, if the products are in a more stable form than the reactants, then heat would be released. On the other hand, if the reactants are more stable than the products, then heat would be required to make that happen.
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