## Relationship between entropy and spontaneity

Mary Becerra 2D
Posts: 53
Joined: Fri Sep 29, 2017 7:06 am

### Relationship between entropy and spontaneity

In Friday's lecture, Lavelle had on is powerpoint, "In any spontaneous process there is an increase in entropy." Does this mean that in any non-spontaneous process there is a decrease in entropy?

Nisarg Shah 1C
Posts: 54
Joined: Sat Jul 22, 2017 3:00 am

### Re: Relationship between entropy and spontaneity

Not necessarily, as we learn later, Gibbs Free Energy or ($\Delta$G) determines the spontaneity of a reaction. It is determined by change in enthalpy, absolute temperature, and entropy: $\Delta G = \Delta H - T\Delta S$. If ($\Delta$G) is negative, the reaction is spontaneous.

Srbui Azarapetian 2C
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### Re: Relationship between entropy and spontaneity

To add to the previous answer, the spontaneity, or Gibbs free energy depends on entropy and enthalpy. Positive entropy and negative enthalpy means the reaction is spontaneous at all temperatures. Positive entropy and enthalpy means the reaction is spontaneous at high temperatures. Negative entropy and enthalpy means the reaction is spontaneous at low temperatures. Negative entropy and positive enthalpy means the reaction is not spontaneous at any temperature.

Cyianna 2F
Posts: 34
Joined: Wed Nov 16, 2016 3:04 am

### Re: Relationship between entropy and spontaneity

Spontaneity refers to any reaction that favors products over reactants. Because so much energy is used to make the products, there's always going to be a decrease in free energy (Gibbs free energy). That is why $\Delta G$ is negative. Entropy must stay positive (or increase) in order to keep $\Delta G$ negative.

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