Define Gibb's free-energy change. Write the mathematical relation to predict the spontaneity.

How is spontaneity of a reaction predicted in light of free energy change, enthalpy change and entropy change?

What is meant by free-energy change?

Write the relation between entropy and enthalpy change. How does this relation help in predicting the spontaneity of a reaction?

How it is related with enthalpy change and entropy change? How would you predict whether a reaction is spontaneous, non spontaneous and equilibrium in term of free energy change?