A researcher estimates for dissolving carbon dioxide in ethanol by adding the…
CHEMISTRY · Single correct · A Level · Chemistry · Thermodynamics · Thermodynamics
Problem
A researcher estimates ΔGdiss∘ for dissolving carbon dioxide in ethanol by adding the gas–phase enthalpy of mixing to the translational entropy of the solute molecules and obtains a strongly negative value. Experimental data, however, show the process is only mildly favorable. Which of the following critiques of the researcher’s approach is most valid?
(a) The translational entropy of a gas is always zero at 298K, so including it exaggerates the entropy term.
(b) Because dissolution occurs at constant pressure rather than constant volume, the researcher should have used ΔU instead of ΔH in calculating ΔG∘.
(c) The calculation ignores specific solvent–solute interactions, such as hydrogen bonding, that can offset the favorable translational entropy.
(d) Gas–phase enthalpies are inherently smaller in magnitude than solution-phase enthalpies, so they should have been multiplied by the dielectric constant of ethanol.