Gibbs and Helmholtz functions as work

However, we must first distinguish between total work and useful work. Chemical systems undergoing change (i.e., in which reactions occur) can do various kinds of work. For instance, batteries can do electrical work. While undergoing these reactions, the chemical system invariably has some change in volume, because it is most unlikely that the reaction products would have exactly the same volume as the reactants. This change in volume AV takes place under some ambient pressure P, so that PAV work is done during the 

The maximum amount of work, other than the work done by the confining pressure, available from reaction (2.2) is 

By comparison, PAV work done by atmospheric pressure during this reaction is 1.61Jmol .  

However, don t forget that according to our sign convention, -w is the work done by a system, or available from a system, so we should perhaps write 

This result is not surprising, as it agrees with our conclusion in 4.10, but it does serve to link the Gibbs energy with an intuitive concept, the available work. 

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