Tetrabutylammonium nitrate,

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

Problem

Tetrabutylammonium nitrate, (C4H9)4NNO3\mathrm{(C_4H_9)_4NNO_3}, is an ionic compound that behaves as a room-temperature ionic liquid when dissolved in water. Its standard thermodynamic parameters for dissolution are ΔHsoln∘=+14.2 kJ mol−1\Delta H^\circ_{\text{soln}} = +14.2\,\text{kJ}\,\text{mol}^{-1} ΔSdiss∘=+118 J mol−1 K−1\Delta S^\circ_{\text{diss}} = +118\,\text{J}\,\text{mol}^{-1}\,\text{K}^{-1} Assume that both values are temperature-independent over the range considered. (1) Part 1: (a) Calculate the standard free-energy change, ΔGsoln∘\Delta G^\circ_{\text{soln}}, for dissolution of tetrabutylammonium nitrate at 298 K298\,\text{K}. (2) Part 2: (b) Determine the temperature (in ∘C^\circ\text{C}) at which ΔGsoln∘\Delta G^\circ_{\text{soln}} becomes zero for this process. (3) Part 3: (c) Explain, in terms of competing energetic factors, why increasing temperature favors dissolution for this compound.

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