What is Gibbs free energy?
A. The energy lost as heat to the surrounding molecules
B. The usable energy released or absorbed by a reaction
C. The energy in the form of kinetic energy in a system
D. The energy contained within the bonds of molecules
The correct answer is B. Gibbs free energy refers to the usable energy released or absorbed by a reaction. It is a thermodynamic quantity that helps determine whether a chemical reaction will occur spontaneously or not. To understand how to calculate Gibbs free energy, you need to know the equation:
ΔG = ΔH - TΔS
where ΔG is the Gibbs free energy change, ΔH is the change in enthalpy (heat) of the system, T is the temperature in Kelvin, and ΔS is the change in entropy (disorder) of the system.
The equation shows that Gibbs free energy takes into account both the enthalpy change and the entropy change of a system during a chemical reaction. If the value of ΔG is negative, it indicates that the reaction can proceed spontaneously, releasing usable energy. On the other hand, if ΔG is positive, the reaction is not spontaneous and requires an input of energy to occur.
So, to determine the Gibbs free energy of a reaction, you need to know the enthalpy change and the entropy change, along with the temperature. By comparing the magnitudes of these values, you can predict whether a reaction is thermodynamically favorable or not, and thus understand the usable energy released or absorbed by the reaction.