Exothermic vs. Endothermic reactions

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Noe BM 1J
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Exothermic vs. Endothermic reactions

Postby Noe BM 1J » Wed Jan 22, 2020 6:20 pm

Does anyone know if we will be asked on the test whether a reaction is exothermic or endothermic? If so, will the delta H value be given to us?

Julie_Reyes1B
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Re: Exothermic vs. Endothermic reactions

Postby Julie_Reyes1B » Wed Jan 22, 2020 7:06 pm

Yes, it can be asked in terms of Le Chatelier's principle. I.e. what happens when you raise the temperature on an endothermic/exothermic reaction. They might give you a reaction and then ask whether it is endothermic or exothermic, then ask questions about Le Chatelier's. For this, they would have to give you a ∆H value.

Wendy Perez 1E
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Re: Exothermic vs. Endothermic reactions

Postby Wendy Perez 1E » Wed Jan 22, 2020 7:21 pm

It is possible. All I suggest knowing is that when delta H is positive, the reaction is endothermic and when delta H is negative, the reaction is exothermic.

Matthew Tsai 2H
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Re: Exothermic vs. Endothermic reactions

Postby Matthew Tsai 2H » Thu Jan 23, 2020 12:17 am

A question that asks if a reaction is endothermic or exothermic should provide delta H, in which if delta H is positive, the reaction is endothermic and if it is negative, the reaction is exothermic.

Junwei Sun 4I
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Re: Exothermic vs. Endothermic reactions

Postby Junwei Sun 4I » Thu Jan 23, 2020 12:18 am

It is possible in the context of the Le Chatelier's principle. For example how will the equilibrium shift if temperature is increased/decreased given a reaction is endothermic or exothermic.

Caroline Beecher 2H
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Re: Exothermic vs. Endothermic reactions

Postby Caroline Beecher 2H » Thu Jan 23, 2020 9:30 am

It is also good to note that when a reaction requires heat (endothermic) while forming product, then heating will favor product formation. When a reaction gives off heat (exothermic) while forming product, then heating will favor reactant formation.

LNgo 1G
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Re: Exothermic vs. Endothermic reactions

Postby LNgo 1G » Thu Jan 23, 2020 9:43 am

If it is asking about temperature effects/changes, I would assume that either endo/exothermic or the delta H value will be given and you can determine the other by knowing that exothermic reactions have a negative delta H value and endothermic reactions have a positive delta H value.

Abby Soriano 1J
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Re: Exothermic vs. Endothermic reactions

Postby Abby Soriano 1J » Thu Jan 23, 2020 12:06 pm

You should expect to know how to determine if a reaction is exothermic or endothermic based on the value of delta H (a negative value signifies an exothermic reaction), the reaction's response to added heat (does the addition of heat cause the reaction to favor the left or right), and the stability of the reactants and products.

Celena Kim 2I
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Re: Exothermic vs. Endothermic reactions

Postby Celena Kim 2I » Thu Jan 23, 2020 4:19 pm

Yes, the problem will typically give you delta H when asked if the reaction is exothermic or endothermic.

Diana Andrade_4F
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Re: Exothermic vs. Endothermic reactions

Postby Diana Andrade_4F » Thu Jan 23, 2020 4:24 pm

Yes, you should be able to determine if the reaction is exothermic or endothermic when given delta H.

Connor Chappell 2B
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Re: Exothermic vs. Endothermic reactions

Postby Connor Chappell 2B » Thu Jan 23, 2020 4:26 pm

The problem given on the tests gives you the chemical equation and the delta H value (change in enthalpy) and you are asked whether the reaction is endothermic or exothermic. If delta H is negative, the reaction is exothermic, and the contrapositive is true.

Madelyn Romberg 1H
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Re: Exothermic vs. Endothermic reactions

Postby Madelyn Romberg 1H » Thu Jan 23, 2020 6:30 pm

From our current tools given, he will give the change in enthalpy and from that information you will have to determine if it is exo/endo, and he may ask questions that utilize Le Chateliers principle in regards to temp.

MTanikella_1K
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Re: Exothermic vs. Endothermic reactions

Postby MTanikella_1K » Fri Jan 24, 2020 2:42 pm

It is a fair question to expect on Test 1. If a reaction is exothermic, delta H will be negative as heat is released while a reaction that is endothermic will have a positive delta H as heat is needed.


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