Question

Can free energy be negative?

Answer 1

Free energy is basically a thermodynamic concept used in thermodynamics of chemical or thermal processes in engineering branches and also in science. Thermo basically refers to the term heat or energy so in this branch we study about the terms related with heat or energy.

Complete step-by-step answer: Free energy can be defined as the maximum useful work done by a compound at constant temperature and constant volume in a reversible phase which is proportional to the negative change in the free energy of Helmholtz equation where Helmontz equation can be represented as $\Delta H=\Delta U+T\Delta S$, where $\Delta H$ shows change in enthalpy, $\Delta U$ change in internal energy, T is temperature and $\Delta S$ change in entropy.
The free energy can also be defined as the maximum useful work at constant temperature and constant pressure. This flow of energy is in the form of either work or fire. So we can conclude that any change in a system can be calculated by its free energy with the sum of the heat and the work. A negative value indicates that the final energy is smaller than the original energy. If any process releases free energy and the reaction is random in nature then G must be negative.
Hence we can say that free energy can be negative.

Note: If H is negative and S is positive then sign of G will also be negative and at both temperatures the reaction will be random in nature. This concludes that all driving forces are in favor of product formation.