Once More on Dg of Chemical Reaction

In a chemical thermodynamics course many students have difficulty understanding the following equation o DG = RT ln K (1) p Even gifted students find it difficult to understand the delta function and the dimensions of K . p The ambiguity of the delta symbol in chemical thermodynamics is the major contributing factor to this lack of understanding. The IUPAC Commission on Physicochemical Symbols in their so-called green book (1) wrote to this end (the IUPAC commission used the symbol H, we have substituted G for H): Although symbols such as D G should denote the integral Gibbs r energy of reaction D G = G(x ) G(x ) (2) r 2 1 in practice this symbol is usually used to denote the change divided by the amount transfered, i.e. the change per extent of reaction, defined by the equation D G = S n m = (dG/dx) (3) r i i i T,p The quantity (dG/dx) will be referred to as the partial change in the Gibbs energy. Over the last twenty years much attention has been paid in this journal to eq 1 (2 13). Authors seeking to