OnlineCBT
Chemistry · THERMODYNAMICS
हिन्दीUsing the mean bond enthalpy values: \( \Delta_{\text{C}-\text{C}} H^\ominus = 347\text{ kJ mol}^{-1} \), \( \Delta_{\text{C}=\text{C}} H^\ominus = 611\text{ kJ mol}^{-1} \), \( \Delta_{\text{C}-\text{H}} H^\ominus = 414\text{ kJ mol}^{-1} \), and \( \Delta_{\text{H}-\text{H}} H^\ominus = 435.8\text{ kJ mol}^{-1} \), what is the standard enthalpy of reaction for the hydrogenation of ethene: \( \text{CH}_2=\text{CH}_2(g) + \text{H}_2(g) \rightarrow \text{CH}_3-\text{CH}_3(g) \)?
Correct answer · Option 1
\( -128.2\text{ kJ mol}^{-1} \)
Explanation
\( \Delta_r H^\ominus = [\text{B.E.}(\text{C}=\text{C}) + \text{B.E.}(\text{H}-\text{H}) + 4\text{B.E.}(\text{C}-\text{H})] - [\text{B.E.}(\text{C}-\text{C}) + 6\text{B.E.}(\text{C}-\text{H})] = [611 + 435.8] - [347 + 2(414)] = 1046.8 - 1175 = -128.2\text{ kJ mol}^{-1} \).
