Exothermic vs Endothermic

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Noh_Jasmine_1J
Posts: 71
Joined: Fri Sep 28, 2018 12:15 am

Exothermic vs Endothermic

Postby Noh_Jasmine_1J » Tue Jan 22, 2019 8:43 am

I know that you can figure out which way the rxn will favor if you know whether it's endothermic or exothermic, but how can you figure that out?

EllerySchlingmann1E
Posts: 76
Joined: Fri Sep 28, 2018 12:24 am

Re: Exothermic vs Endothermic

Postby EllerySchlingmann1E » Tue Jan 22, 2019 8:52 am

For these types of questions, the change in enthalpy (delta H) will probably be given. In that case, positive delta H indicates an endothermic reaction and negative delta H indicates an exothermic reaction. However, a more challenging question may talk about a combustion reaction, which you have to infer is exothermic because heat is released, or a synthesis reaction (2N=>N2) which is likely endothermic because it requires energy.

Ryan Danis 1J
Posts: 66
Joined: Fri Sep 28, 2018 12:18 am

Re: Exothermic vs Endothermic

Postby Ryan Danis 1J » Tue Jan 22, 2019 9:06 pm

Usually delta H is given and you can tell by its sign. If delta H positive it’s endothermic, if delta H is negative it’s exothermic.

marisaimbroane1J
Posts: 69
Joined: Fri Sep 28, 2018 12:23 am

Re: Exothermic vs Endothermic

Postby marisaimbroane1J » Tue Jan 22, 2019 9:41 pm

You can think of heat as a reactant in an endothermic rxn and a product in an exothermic rxn. With this in mind, you can use Le Chatelier's Principle in the same was as if you were increasing or decreasing the amount of product or reactant. (Like how if you decrease heat in an endothermic rxn, it is like decreasing the amount of reactant--- therefore, reactants are favored).

Rosha Mamita 2H
Posts: 63
Joined: Fri Sep 28, 2018 12:19 am

Re: Exothermic vs Endothermic

Postby Rosha Mamita 2H » Tue Jan 22, 2019 10:36 pm

It wont automatically favor a certain direction based on whether the equation is endothermic or exothermic, but increasing and decreasing the heat term will cause the reaction to favor a certain side. An endothermic reaction has the heat term on the left side and an exothermic reaction has the heat term on the right side. Increasing the heat term shifts the reaction to the side without the term and decreasing the term shifts the reaction to the side with the term.


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