Chemistry

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)

\Delta G_{\text{rxn}}^{\circ}=+173.0\,\text{kJ}

Reaction B: 2 NO(g) + O₂(g) → 2 NO₂(g)

\Delta G_{\text{rxn}}^{\circ}=−72.0\,\text{kJ}

Selected formation values: Species (state)

\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) a. Using Reactions A and B, determine the standard Gibbs free energy of formation of NO₂(g). Show all steps in your reasoning. b. Calculate

\Delta G_{\text{rxn}}^{\circ}

for the acid-rain reaction above. c. Assess whether the acid-rain reaction is thermodynamically favorable under standard conditions and explain the environmental significance of your result.

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