Exo/Endo-thermic Rxns

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Jose Robles 1D
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Joined: Fri Aug 02, 2019 12:15 am

Exo/Endo-thermic Rxns

Postby Jose Robles 1D » Sun Jan 19, 2020 7:11 pm

Can someone tell me which applies to products? And reactants? How do you detect this in an equation(please give example if possible)?

JonathanS 1H
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Joined: Thu Jul 11, 2019 12:17 am

Re: Exo/Endo-thermic Rxns

Postby JonathanS 1H » Sun Jan 19, 2020 7:17 pm

I'm not quite sure what you are exactly asking, but the endothermic/exothermic reactions refers to the reaction requiring or releasing heat. Endothermic reactions require heat to occur, while exothermic reactions release heat as a product.

CalvinTNguyen2D
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Joined: Thu Jul 25, 2019 12:16 am

Re: Exo/Endo-thermic Rxns

Postby CalvinTNguyen2D » Sun Jan 19, 2020 9:09 pm

I'm not 100% sure I understand the question, but relating to chemical equilibrium, Exothermic reactions will have heat as a "product" as they release heat during their reaction, while Endothermic reactions will have heat as a "reactant" as it absorbs heat during the reaction. This will be indicated in the problem; we can predict equilibrium shifts with temperature by following Le Chatelier's Principle- if the reactions is exothermic, and heat is added, then the reaction shifts to the left, and vice-versa. Hope this helps!

KSong_1J
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Joined: Thu Jul 11, 2019 12:17 am

Re: Exo/Endo-thermic Rxns

Postby KSong_1J » Sun Jan 19, 2020 9:10 pm

Endothermic reactions absorb energy to create products while exothermic products release energy when creating products. An example that combines this idea with Le Chatelier’s principle is if you raised the temperature in a reaction; if it’s an endothermic reaction, a higher temperature will cause the equilibrium to shift towards products and if it’s exothermic, it will tend to favor reactants.

Janet Nguy 2C
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Joined: Sat Aug 24, 2019 12:17 am

Re: Exo/Endo-thermic Rxns

Postby Janet Nguy 2C » Sun Jan 19, 2020 9:12 pm

If the topic of exothermic/endothermic reactions were to come up in a test question, it would probably either tell you explicitly if the reaction was exo/endothermic OR it'll give you the delta H value (aka change in enthalpy), and from there you could decide if it was exothermic or endothermic. If delta H > 0 (is positive) then the reaction is endothermic, and if delta H < 0 (is negative), then the reaction is exothermic.

You can also think about it like this:

Endothermic: R + heat -> P
Exothermic: R -> P + heat

Ashley Nguyen 2L
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Re: Exo/Endo-thermic Rxns

Postby Ashley Nguyen 2L » Sun Jan 19, 2020 9:24 pm

If the reaction is endothermic (requires heat), pretend like heat is a reactant in the equation. [ A + B + heat -> C ] From here, you can treat an increase/decrease in temperature as an increase/decrease in reactant. If temperature increases in an endothermic reaction, then the reaction will shift right towards the products. If the temperature decreases, then the reaction will shift to the left towards the reactants.

If the reaction is exothermic (releases heat)< pretend like heat is a product. [ A + B -> C + heat ] Similar to the above statement, you can treat an increase/decrease in temperature as an increase/decrease in product. If temperature increases in an exothermic reaction, the reaction will shift left towards the reactants. If the temperature decreases, then the reaction will shift to the right towards the reactants.


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