From the following data at , which of the following statement(s) is/are correct?<br><br><br><br> — Thermodynamics and Thermochemistry Chemistry Question
Question
From the following data at $25^\circ\text{C}$, which of the following statement(s) is/are correct?<br>$1/2\text{H}_2\text{(g)} + 1/2\text{O}_2\text{(g)} \to \text{OH(g)}; \Delta H^\circ = 42\text{ kJ}$<br>$\text{H}_2\text{(g)} + 1/2\text{O}_2\text{(g)} \to \text{H}_2\text{O(g)}; \Delta H^\circ = -242\text{ kJ}$<br>$\text{H}_2\text{(g)} \to 2\text{H(g)}; \Delta H^\circ = 436\text{ kJ}$<br>$\text{O}_2\text{(g)} \to 2\text{O(g)}; \Delta H^\circ = 495\text{ kJ}$
💡 Solution & Explanation
Atomization of $\text{H}_2\text{O(g)} = -\Delta H_f(\text{H}_2\text{O}) + \text{Atomization}(\text{H}_2) + 0.5\times\text{Atomization}(\text{O}_2) = 242 + 436 + 247.5 = 925.5\text{ kJ}$. $\Delta H_f(\text{H(g)}) = 436/2 = +218\text{ kJ/mol}$ (c is wrong). Equation 1 directly denotes the formation of OH(g), so 42 kJ/mol is correct.