A computational model estimates the following thermodynamic quantities for the…

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

Problem

A computational model estimates the following thermodynamic quantities for the dissolution of LiBr in liquid methanol at 298 K298\,\text{K}: Estimated enthalpy change: ΔHest∘=−75 kJ mol−1\Delta H^\circ_{\text{est}} = -75\,\text{kJ mol}^{-1} Estimated entropy change: ΔSest∘=+150 J mol−1 K−1\Delta S^\circ_{\text{est}} = +150\,\text{J mol}^{-1}\,\text{K}^{-1} The experimentally measured standard free energy of dissolution is ΔGexp∘=+2 kJ mol−1\Delta G^\circ_{\text{exp}} = +2\,\text{kJ mol}^{-1}. (a) Using the estimated values, calculate ΔGest∘\Delta G^\circ_{\text{est}} at 298 K298\,\text{K}. (b) Quantify the discrepancy between ΔGest∘\Delta G^\circ_{\text{est}} and ΔGexp∘\Delta G^\circ_{\text{exp}}. Express your answer as both an absolute difference and as a percentage of ∣ΔGexp∘∣|\Delta G^\circ_{\text{exp}}|. (c) Identify two physical factors not captured in the model that could account for the difference between the estimated and experimental free energies, and briefly explain the role each factor plays. (d) Recommend a single, specific experimental measurement that would supply data to refine the computational model, and justify how the data would reduce uncertainty in the predicted ΔG∘\Delta G^\circ.

Related theory

Browse the problem library