Exothermic/Endothermic  [ENDORSED]

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Postby donnanguyen1d » Sun Dec 03, 2017 12:05 pm

How do you know if a reaction is exothermic or endothermic without being told?

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Re: Exothermic/Endothermic

Postby sofiakavanaugh » Sun Dec 03, 2017 12:42 pm

Unless I am mistaken, you would have to be given some sort of other information. The enthalpies, for example, or be told if the reaction requires energy (endothermic) or releases energy (exothermic). Also you know that combustion reactions are always exothermic.

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Re: Exothermic/Endothermic  [ENDORSED]

Postby Chem_Mod » Sun Dec 03, 2017 2:06 pm

Simple reactions involving only bond breaking are always endothermic.
We know this in Chem 14A as we discussed bond enthalpies.

For example: Cl2(g) ---> 2Cl(g)

In Chem 14B I will show you how to calculate reaction enthalpies.

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