Which of the following best explains why the sign of for many crystalline solids in…

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

Problem

Which of the following best explains why the sign of

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

for many crystalline solids in water is difficult to predict from tabulated thermodynamic data alone? (a) Because lattice enthalpy is not included in standard enthalpy of formation tables, calculated values of

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

are highly uncertain. (b) Because standard molar entropies for many aqueous ions are unavailable, the

T\Delta S^{\circ}

term cannot be evaluated accurately. (c) Because large but opposite

\Delta H^{\circ}

and

T\Delta S^{\circ}

terms nearly cancel, small data errors can change the sign of

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

.},{ (d) Because ionic activity coefficients deviate from unity, the tabulated standard‐state values of

\Delta G^{\circ}

are invalid for dissolution processes.

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