Question
Consider the $$\Delta G_f^ \circ $$ and $$\Delta H_f^ \circ \left( {kJ/mol} \right)$$ for the following oxides. Which oxide can be most easily decomposed to form the metal and oxygen gas?
A.
$$ZnO\left( {\Delta {G^ \circ } = - 318.4,\Delta {H^ \circ } = - 348.3} \right)$$
B.
$$C{u_2}O\left( {\Delta {G^ \circ } = - 146.0,\Delta {H^ \circ } = - 168.8} \right)$$
C.
$$HgO\left( {\Delta {G^ \circ } = - 58.5,\Delta {H^ \circ } = - 90.8} \right)$$
D.
$$PbO\left( {\Delta {G^ \circ } = - 187.9,\Delta {H^ \circ } = - 217.3} \right)$$
Answer :
$$HgO\left( {\Delta {G^ \circ } = - 58.5,\Delta {H^ \circ } = - 90.8} \right)$$
Solution :
$$\eqalign{
& \Delta {G^ \circ } = - RT\,\,{\text{ln}}\,K; \cr
& K \uparrow {\text{stability}}\,{\text{of}}\,{\text{reactant}} \downarrow \cr} $$