Sign of Gibbs Free Energy, ?G
change in Gibbs free energy =
(total free energy change for system - free energy lost in disordering the system)
If reaction is exothermic (DHo is -ve) and
entropy increases (DSo is +ve), then
DGo must be -ve and reaction CAN proceed.
If reaction is endothermic (DHo is +ve), and
entropy decreases (DSo is -ve), then
DGo must be +ve; reaction CANNOT proceed.