Chem thermo III Flashcards
What does ∆G tell us?
If a reaction is spontaneous or not
What tells us if reaction is spontaneous?
If ∆G is more -ve
What tells us if reaction is at equilibrium?
If ∆G = 0
What does the magnitude of ∆G tell us?
How far a spontaneous process proceeds towards completion
If ∆H is +ve and ∆S is is +ve
spontaneous under high temps and non under low temps
If ∆H is -ve and ∆S is is +ve
Spontaneous reaction
If ∆H is +ve and ∆S is is -ve
Non-spontaneous reaction
If ∆H is -ve and ∆S is is -ve
spontaneous under low temps and non under high temps
What is a coupled reaction?
When a spontaneous reaction is used to drive a non-spontaneous reaction
How does coupled reactions work in the body?
ATP –> ADP
∆rG = -30.5 kJ/mol
For reactions that have a +ve ∆rG, the energy from ATP is released to the body to be utilised to drive such NS reactions
*ATP ∆rG must be larger than NS +ve ∆rG
What happens at ∆G = 0
No driving force so equilibrium is reached
There is no driving force because Gibbs energy is reached
Key expression
∆rG = ∆rGº + RT lnQ
Key expression under equilibrium
At equilibrium, Q = K
0 = ∆rGº + RT lnK
Therefore, ∆rGº = - RT lnK. We can use this expression to find ∆rGº and sub into original equation
We can also use this to find the spontaneity of the reaction
