9. Choose the correct equation for the standard enthalpy of formation of CO(g), where ΔHf° for CO = –110.5 kJ/mol (gr indicates graphite). (A) 2C(gr) + O2(g) → 2CO(g), ΔH° = –110.5 kJ (B) C(gr) + O(g) → CO(g), ΔH° = –110.5 kJ (C) C(gr) + O2(g) → CO(g), ΔH° = –110.5 kJ (D) C(gr) + CO2(g) → 2CO(g), ΔH° = –110.5 kJ e. CO(g) → C(gr) + O(g), ΔH° = –110.5 kJ