![]() ![]() ![]() Thus although the free energy always falls when a gas expands or a chemical reaction takes place spontaneously, there need be no compensating increase in energy anywhere else. Free Energy is not energy: A much more serious difficulty with the Gibbs function, particularly in the context of chemistry, is that although G has the units of energy (joules, or in its intensive form, J mol –1), it lacks one of the most important attributes of energy in that it is not conserved. Entropy Chemical and physical changes in a system may be accompanied by either an increase or a decrease in the disorder of the system, corresponding to an increase in entropy (S > 0) or a decrease in entropy (S This is most commonly in the form of electrical work (moving electric charge through a potential difference), but other forms of work (osmotic work, increase in surface area) are also possible. In contrast, the entropy change due to solvent reorganization (Snsord) shows a minimum around the critical point where the solvent excess shows a maximum. By "useful", we mean work other than that which is associated with the expansion of the system. The ligand-shell entropy (SL) is shown to be fairly insensitive to variations in solvent density ranging from vacuum to twice the critical density (c). Thus, entropy has the units of energy unit per Kelvin, J K -1. The “free” part of the older name reflects the steam-engine origins of thermodynamics with its interest in converting heat into work: ΔG is the maximum amount of energy which can be “freed” from the system to perform useful work. Thermodynamics may appear at first to be a rather esoteric subject, but when you think about it, almost every chemical (and biological) process is governed by changes in entropy and free energy. Entropy is the amount of energy transferred divided by the temperature at which the process takes place. Qualitatively, entropy is simply a measure how much the energy of atoms and molecules become more spread out in a process and can be defined in terms of statistical probabilities of a system or in terms of the other thermodynamic quantities. Entropy is a thermodynamic quantity that is generally used to describe the course of a process, that is, whether it is a spontaneous process and has a probability of occurring in a defined direction, or a non-spontaneous process and will not proceed in the defined direction, but in the reverse direction. Free Energy is not necessarily "free": The appellation “free energy” for G has led to so much confusion that many scientists now refer to it simply as the Gibbs energy. Entropy is a state function that is often erroneously referred to as the 'state of disorder' of a system. ![]()
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