Chemistry

Problem

The following standard Gibbs free energy changes are measured at 298 K: 1.

\displaystyle \mathrm{C(s,graphite)+O_2(g)\rightarrow CO_2(g)}\qquad \Delta G^\circ=-394.4\,\text{kJ}

\displaystyle \mathrm{CO(g)+\tfrac12 O_2(g)\rightarrow CO_2(g)}\qquad \Delta G^\circ=-257.2\,\text{kJ}

Using only these data, what is the standard Gibbs free energy of formation,

\Delta G_f^\circ

, of CO(g) in kJ mol

^{-1}

? a)

-257\ \text{kJ}

-137\ \text{kJ}

+137\ \text{kJ}

-394\ \text{kJ}