Chemistry - Thermochemistry - Hess's Law - Hess's Law Worked Examples

3 worked examples showing the 'stacking equations' method. Example 1: 'Find ΔH for: C(s) + ½O₂(g) → CO(g). Given: (1) C(s) + O₂(g) → CO₂(g), ΔH₁ = -394 kJ. (2) CO(g) + ½O₂(g) → CO₂(g), ΔH₂ = -283 kJ.' Work: We want C → CO. Take equation (1) as is. REVERSE equation (2): CO₂ → CO + ½O₂, ΔH = +283. ADD