The data below refers to gas phase reaction at constant pressure at .<br><br><br>From these data, th — Thermodynamics and Thermochemistry Chemistry Question
Question
The data below refers to gas phase reaction at constant pressure at $25^\circ\text{C}$.<br>$\text{CH}_3-\text{CH}_3 \to \text{CH}_3-\text{CH}_2^\cdot + \text{H}^\cdot; \Delta H_1 = +420\text{ kJ mol}^{-1}$<br>$\text{CH}_3-\text{CH}_2^\cdot \to \text{CH}_2=\text{CH}_2 + \text{H}^\cdot; \Delta H_2 = +168\text{ kJ mol}^{-1}$<br>From these data, the enthalpy change $\Delta H$ for the reaction: $2\text{CH}_3-\text{CH}_2^\cdot \to \text{CH}_3-\text{CH}_3 + \text{CH}_2=\text{CH}_2$ is
💡 Solution & Explanation
Target reaction can be obtained by adding Eq2 and the reverse of Eq1. $\text{CH}_3-\text{CH}_2^\cdot \to \text{CH}_2=\text{CH}_2 + \text{H}^\cdot$ (168 kJ). $\text{CH}_3-\text{CH}_2^\cdot + \text{H}^\cdot \to \text{CH}_3-\text{CH}_3$ (–420 kJ). Sum = $168 - 420 = -252\text{ kJ}$.