Nitrogen oxides participate in the formation of acid rain

CHEMISTRY · Multi-part · A Level · Chemistry · Thermodynamics · Thermodynamics

Problem

Nitrogen oxides participate in the formation of acid rain. The following data are available at 298 K. Reaction A: N₂(g) + O₂(g) → 2 NO(g) ΔGrxn∘=+173.0 kJ\Delta G_{\text{rxn}}^{\circ}=+173.0\,\text{kJ} Reaction B: 2 NO(g) + O₂(g) → 2 NO₂(g) ΔGrxn∘=−72.0 kJ\Delta G_{\text{rxn}}^{\circ}=−72.0\,\text{kJ} Selected formation values: Species (state) ΔGf∘\Delta G_f^{\circ} (kJ mol⁻¹) NO(g) +87.6 H₂O(l) −237.1 HNO₃(aq) −207.4 N₂(g), O₂(g) 0 The aqueous reaction producing nitric acid is 3 NO₂(g) + H₂O(l) → 2 HNO₃(aq) + NO(g) (1) Using Reactions A and B, determine the standard Gibbs free energy of formation of NO₂(g). Show all steps in your reasoning. (2) Calculate ΔGrxn∘\Delta G_{\text{rxn}}^{\circ} for the acid-rain reaction above. (3) Assess whether the acid-rain reaction is thermodynamically favorable under standard conditions and explain the environmental significance of your result.

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