# Entropy and Gibbs free energy

Discussion in 'MCAT Study Question Q&A' started by Hemichordate, Jul 11, 2010.

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1. ### HemichordatePeds 7+ Year Member

May 5, 2008
If entropy dictates the direction of a reaction, do enthalpy and gibbs free energy dictates how fast the reaction proceeds in that direction?

3. ### loveoforganic-Account Deactivated- 2+ Year Member

Jan 30, 2009
I think you're a bit confused, but I may just be misunderstanding what you're asking.

Changes in entropy and enthalpy are the two factors (along with temperature) that give you your gibbs free energy change for a given reaction (the favorability of a reaction). This is generally referred to as the thermodynamics of a reaction.

The rate of reaction is determined by the order of the reaction, the temperature, and the activation energy of the reaction. This is generally referred to as the kinetics of a reactions.

There is not necessarily a relationship between favorability and rate.

4. ### HemichordatePeds 7+ Year Member

May 5, 2008
I guess I'm just wondering if entropy is the sole factor that usually determines the direction of a reaction.

5. ### RogueUnicornrawr. 7+ Year Member

9,616
1,173
Jul 15, 2009
no gibbs free energy is.

6. ### loveoforganic-Account Deactivated- 2+ Year Member

Jan 30, 2009
This. dG = dH - TdS

Your dG value ultimately tells you the favorability of a reaction.

dH, T, and dS are factors that tell you your dG value.