Use these three reactions



CH4(g) + 2 O2(g) −→ CO2(g) + 2 H2O(g) ∆H◦ = −802 kJ

CH4(g) + CO2(g) −→ 2 CO(g) + 2 H2(g) ∆H◦ = 247 kJ

CH4(g) + H2O(g) −→ CO(g) + 3 H2(g) ∆H◦ = 206 kJ



to determine the appropriate enthalpy change of



CH4(g) + 3/2 O2(g) −→ CO(g) + 2 H2O(g).