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

Do not give me a website to look at.

The Gibbs free energy (G) is a concept in thermodynamics that describes the maximum amount of usable energy released or absorbed by a chemical reaction at constant temperature and pressure. It is denoted as ΔG and is calculated using the equation ΔG = ΔH - TΔS, where ΔH is the change in enthalpy, T is the temperature in Kelvin, and ΔS is the change in entropy.

To understand Gibbs free energy, we need to have some knowledge of entropy and enthalpy:

1. Enthalpy (ΔH): It represents the heat energy change in a reaction. Positive ΔH values indicate endothermic reactions (energy is absorbed), while negative ΔH values indicate exothermic reactions (energy is released).

2. Entropy (ΔS): It is a measure of the disorder or randomness of a system. Positive ΔS values indicate an increase in disorder, while negative ΔS values indicate a decrease in disorder.

Now, back to Gibbs free energy (ΔG). The equation ΔG = ΔH - TΔS tells us that the change in Gibbs free energy is determined by the enthalpy and entropy changes in a reaction. If the value of ΔG is negative, it means that the reaction is spontaneous, releases usable energy, and tends to proceed forward. On the other hand, if ΔG is positive, the reaction is non-spontaneous, requires an input of energy, and tends to proceed in the reverse direction. If ΔG is zero, the reaction is at equilibrium.

So, to answer the question, Gibbs free energy (option B) corresponds to the usable energy released or absorbed by a reaction. It is not the energy lost as heat to the surrounding molecules (option A), the energy in the form of kinetic energy in a system (option C), or the energy contained within the bonds of molecules (option D).

B. The usable energy released or absorbed by a reaction