A theoretical model predicts a strongly negative for in water by summing lattice…

CHEMISTRY · Single correct · A Level · Chemistry · Thermodynamics · Thermodynamics

Problem

A theoretical model predicts a strongly negative

\Delta G^{\circ}_{\text{diss}}

for

\mathrm{MgSO_4(s)}

in water by summing lattice enthalpy and ion–water interaction energies, yet the measured solubility at

25\,^{\circ}\!\text{C}

is modest. Which additional quantity, if included, would most improve the predictive power of the model? (a) The dielectric constant of water at

25\,^{\circ}\text{C}

. (b) The enthalpy of vaporization of water at

25\,^{\circ}\text{C}

. (c) The entropy change associated with restructuring of water molecules around

\mathrm{Mg^{2+}}

and

\mathrm{SO_4^{2-}}

. (d) The pH of the

\mathrm{MgSO_4(aq)}

solution at equilibrium.