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### Finding whether exothermic or Endothermic

Posted: Sun Feb 09, 2020 12:55 pm
Are we going to be able to know if a reaction is exothermic or endothermic if the delta H isn't given? If so, how?

### Re: Finding whether exothermic or Endothermic

Posted: Sun Feb 09, 2020 12:59 pm
One of the ways you can tell if an equation is exothermic or endothermic is using Gibbs Free Energy.
If the $\Delta G$ is negative then it is exothermic, if it is positive then it is endothermic.

### Re: Finding whether exothermic or Endothermic

Posted: Sun Feb 09, 2020 8:30 pm
Note that exothermic/endothermic refers to heat (exergonic/endergonic refers to free energy). Although exothermic reactions usually have a positive delta G, it's not always the case.
By definition a system is exothermic when the delta H is negative, and endothermic when the delta H is positive

### Re: Finding whether exothermic or Endothermic

Posted: Sun Feb 09, 2020 8:37 pm
Another giveaway is the phases of the reactants and products. For example, if the reactant is a solid and both products are liquids, it's most likely endothermic

### Re: Finding whether exothermic or Endothermic

Posted: Sun Feb 09, 2020 8:41 pm
You can also tell by the reactions. For example a solid going to liquids or gas. You need heat to provide energy to break up intermolecular forces and thus the reaction is endothermic. Try thinking about the forces and bonds and how you need energy to break them