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Gibbs Free-Energy and Entropy Change
Physical
A2
Born-Haber
AQA Content
Calculate entropy changes from absolute entropy values
Use the relationship ∆G = ∆H – T∆S to determine how ∆G varies with temperature
Use the relationship ∆G = ∆H – T∆S to determine the temperature at which a reaction becomes feasible.
Specification Notes
∆H, whilst important, is not sufficient to explain feasible change.
The concept of increasing disorder (entropy change, ∆S).
∆S accounts for the above deficiency, illustrated by physical changes and chemical changes.
The balance between entropy and enthalpy determines the feasibility of a reaction given by the relationship:
∆G = ∆H – T∆S (derivation not required).
For a reaction to be feasible, the value of ∆G must be zero or negative.
Notes
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