The values of are very important in metallurgy. The values for the following reactions at 1000 K are — Thermodynamics and Thermochemistry Chemistry Question
Question
The values of $\Delta G$ are very important in metallurgy. The $\Delta G$ values for the following reactions at 1000 K are given as:<br>$\text{S}_2\text{(s)} + 2\text{O}_2\text{(g)} \to 2\text{SO}_2\text{(g)}; \Delta G = -544\text{ kJ}$<br>$2\text{Zn(s)} + \text{S}_2\text{(s)} \to 2\text{ZnS(s)}; \Delta G = -293\text{ kJ}$<br>$2\text{Zn(s)} + \text{O}_2\text{(g)} \to 2\text{ZnO(s)}; \Delta G = -480\text{ kJ}$<br>The $\Delta G$ for the reaction:<br>$2\text{ZnS(s)} + 3\text{O}_2\text{(g)} \to 2\text{ZnO(s)} + 2\text{SO}_2\text{(g)}$ will be
💡 Solution & Explanation
Using Hess's law on $\Delta G$: Reaction 1: $\text{S}_2 + 2\text{O}_2 \to 2\text{SO}_2$ ($\Delta G = -544$). Reaction 2 (reversed): $2\text{ZnS} \to 2\text{Zn} + \text{S}_2$ ($\Delta G = +293$). Reaction 3: $2\text{Zn} + \text{O}_2 \to 2\text{ZnO}$ ($\Delta G = -480$). Sum = $2\text{ZnS} + 3\text{O}_2 \to 2\text{ZnO} + 2\text{SO}_2$. $\Delta G = -544 + 293 - 480 = -731\text{ kJ}$.