## Finding whether exothermic or Endothermic

$\Delta S = \frac{q_{rev}}{T}$

Rita Chen 1B
Posts: 112
Joined: Sat Jul 20, 2019 12:15 am

### Finding whether exothermic or Endothermic

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?

TimVintsDis4L
Posts: 104
Joined: Sat Aug 17, 2019 12:17 am

### Re: Finding whether exothermic or Endothermic

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.

Frank He 4G
Posts: 50
Joined: Tue Nov 12, 2019 12:19 am

### Re: Finding whether exothermic or Endothermic

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

SarahCoufal_1k
Posts: 102
Joined: Thu Jul 25, 2019 12:17 am

### Re: Finding whether exothermic or Endothermic

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

MaggieHan1L
Posts: 100
Joined: Thu Jul 11, 2019 12:17 am

### Re: Finding whether exothermic or Endothermic

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