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Exothermic vs. Endothermic reactions

Posted: Wed Jan 22, 2020 6:20 pm
by Noe BM 1J
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?

Re: Exothermic vs. Endothermic reactions

Posted: Wed Jan 22, 2020 7:06 pm
by Julie_Reyes1B
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.

Re: Exothermic vs. Endothermic reactions

Posted: Wed Jan 22, 2020 7:21 pm
by Wendy 1E
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.

Re: Exothermic vs. Endothermic reactions

Posted: Thu Jan 23, 2020 12:17 am
by Matthew Tsai 2H
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.

Re: Exothermic vs. Endothermic reactions

Posted: Thu Jan 23, 2020 12:18 am
by Junwei Sun 4I
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.

Re: Exothermic vs. Endothermic reactions

Posted: Thu Jan 23, 2020 9:30 am
by Caroline Beecher 2H
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.

Re: Exothermic vs. Endothermic reactions

Posted: Thu Jan 23, 2020 9:43 am
by LNgo 1G
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.

Re: Exothermic vs. Endothermic reactions

Posted: Thu Jan 23, 2020 12:06 pm
by Abby Soriano 1J
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.

Re: Exothermic vs. Endothermic reactions

Posted: Thu Jan 23, 2020 4:19 pm
by Celena Kim 2I
Yes, the problem will typically give you delta H when asked if the reaction is exothermic or endothermic.

Re: Exothermic vs. Endothermic reactions

Posted: Thu Jan 23, 2020 4:24 pm
by Diana Andrade_4F
Yes, you should be able to determine if the reaction is exothermic or endothermic when given delta H.

Re: Exothermic vs. Endothermic reactions

Posted: Thu Jan 23, 2020 4:26 pm
by Connor Chappell 2B
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.

Re: Exothermic vs. Endothermic reactions

Posted: Thu Jan 23, 2020 6:30 pm
by Madelyn Romberg 1H
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.

Re: Exothermic vs. Endothermic reactions

Posted: Fri Jan 24, 2020 2:42 pm
by MTanikella_1K
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.