Sulfur dioxide reacts with strontium oxide as follows: $$ \mathrm{SO}_{2}(g)+\mathrm{SrO}(g) \longrightarrow \mathrm{SrSO}_{3}(s) $$ (a) Without using thermochemical data, predict whether \(\Delta G^{\circ}\) for this reaction is more negative or less negative than \(\Delta H^{\circ} .\) (b) If you had only standard enthalpy data for this reaction, how would you estimate the value of \(\Delta G^{\circ}\) at \(298 \mathrm{~K},\) using data from Appendix \(\mathrm{C}\) on other substances.

(The standard Gibbs free energy change (∆G°) in a reaction can be expressed as: ∆G° = ∆H° - T∆S° Here, T is the absolute temperature and ∆S° is the standard entropy change. Based on the given reaction, we need to predict if the entropy change (∆S°) will be positive or negative. As we proceed from reactants to products, sulfur dioxide gas and strontium oxide gas react to form a solid, strontium sulfite. In this process, we can assume the entropy change to be negative as going from gaseous to solid state decreases the freedom of movement of particles.)

(Since the entropy change (∆S°) is negative and the temperature (T) is always positive, the term T∆S° is negative. Considering the equation for ∆G°: ∆G° = ∆H° - T∆S° Thus, ∆H° is more negative than ∆G°, implying that ∆G° is less negative than ∆H°.)

(To estimate the value of ∆G° at 298 K, we can use the equation: ∆G° = ∆H° - T∆S° We are given that we only have standard enthalpy data (∆H°). We can assume the entropy change for similar compounds and use that to estimate the value of ∆G° at 298 K. For example, we can look up the standard entropy change for the formation of a similar group 2 metal sulfite and use that value. However, this estimation method has limitations and is not very accurate.) In summary: (a) The standard Gibbs free energy change (∆G°) is less negative than the standard enthalpy change (∆H°). (b) To estimate the value of ∆G° at 298 K using only ∆H° data, we can look at similar compounds and assume an approximate value for the entropy change (∆S°) and use the relation ∆G° = ∆H° - T∆S° to calculate the estimated value. However, this method has limitations and is not very accurate.