ABSTRACT
Recall from Chapter 5 that the equilibrium constant for any reaction can be determined if the standard-state chemical potentials (μ° values) or standard Gibbs free energies of formation (Gfo values) of the reactants and products are known. For the malachite dissolution reaction (Equation 6.3), the Gfo values for Cu2+ (65.52 kJ mol−1), CO32− (−527.9 kJ mol−1), and H2O (−237.141 kJ mol−1)
are obtained from Table 5.5. The Gfo value for malachite (−903.7 kJ mol−1) is obtained from Symes and Kester (1984). The standard free energy change for the reaction is
Δ Δ Δ Δ ΔG G G G Gr f f f malachite
2= + + −+ −2 22 32, , , (6.5)
ΔGfo 12 65 52 527 9 2 237 141 9 3 7 32 56 kJ mol= ( ) + − + − − − = −. ( . ) ( . ) ( . ) .0 (6.6)
Because Gfo is positive, the reaction products (Cu2+, CO32−, and liquid water) are less stable than the reactants (malachite and H+) if the reaction were to occur in the standard state. Using Equation 5.22, the equilibrium constant for malachite dissolution is computed:
log .
