A Simple Analogy of the Relationship of AG" to the Position of Equilibrium Take x piece of string about 3 ft long and put on it a slider (e.g. ring or key). Labelling one hand "pure rcxctants" and the other "pure products", suspend the slider by holding one end of the string in each hand. The position of the slider denotes the position of the equilibrium, either products or reactants predominating in the equilibrium mixture. The vertical separation of the ends of the string denotes either AGO positive ('product' hand higher than 'reactant' hand) or negative ('reactant' hand higher than 'product' hand). If the hands are arranged so that AG" is positive, the slider moves towards the reactant side (Fig. 1) showing reactants predominating in the equilibrium mixture. Conversely, if AGO is negative, products are seen to predominate in the equilibrium mixture (Fig. 2). If the two hands are on the same level, AG" = 0 and the equilibrium mixture is 50-50. The demonstration (obviously carried out at oonstant temperature and pressurel) also shows that the equilibrium state is lower in G than either pure reactants or pure products. Pure Reactants Pure Products
Free Energy
Slider Figure 1.
402 / Journal of Chemical Education
Positive AGO
Slidel Figure 2.
Negative AGO
