The standard free energy change (\( \Delta G^\circ \)) for the following reaction (in kJ) at 25°C is
\[
3Ca(s) + 2 Au^{+}(aq, 1M) \rightleftharpoons 3Ca^{2+}(aq, 1M) + 2Au(s)
\]
(given: \( E^\circ_{{Au}^{3+/2+}} = +1.50 \, V \), \( E^\circ_{{Ca}^{2+/Ca}} = -2.87 \, V \), \( F = 96500 \, {C mol}^{-1} \))