Nitrogen dioxide dimerizes reversibly according to Reaction 1 below, and the dimer can subsequently hydrolyze in water as shown in Reaction 2. All species are at their standard states (298 K, 1 atm, 1 M).
Reaction 1: 2 NO₂(g) ⇌ N₂O₄(g)
Reaction 2: N₂O₄(g) + H₂O(l) → 2 HNO₂(aq)
Overall: 2 NO₂(g) + H₂O(l) → 2 HNO₂(aq)
(a) Predict the sign of ΔS° for Reaction 1 and justify your reasoning in terms of changes in gaseous moles and molecular complexity.
(b) At higher temperatures the equilibrium of Reaction 1 shifts toward NO₂(g). Explain, using entropy arguments, why this temperature dependence is consistent with your prediction in part (a).
(c) Predict and justify the sign of ΔS° for Reaction 2.
(d) Using qualitative reasoning only, decide whether the overall reaction is expected to have a positive, negative, or near-zero ΔS°. Incorporate your analyses from parts (a) and (c) and comment on which step you expect to dominate the overall entropy change.
(a) Predict and justify the sign of ΔS° for Reaction 1.
(b) Explain the temperature dependence of the Reaction 1 equilibrium in terms of entropy.
(d) Predict the sign of ΔS° for the overall reaction and identify which individual reaction has the greater influence on that sign, with justification.