• # question_answer 60) If $\Delta {{H}_{f}}$ of ${{C}_{2}}{{H}_{4}}$ and ${{C}_{2}}{{H}_{6}}$ are ${{x}_{1}}\,and\text{ }{{x}_{2}}$ $Kcal\text{ }mo{{l}^{-1}}$, then heat of hydrogenation of ${{C}_{2}}{{H}_{4}}$ is- A) ${{\text{x}}_{1}}+{{x}_{2}}$B)               ${{x}_{1}}-{{x}_{2}}$C) ${{x}_{2}}-{{x}_{1}}$                       D) ${{x}_{1}}+2{{x}_{2}}$

$~{{C}_{2}}{{H}_{4}}\,\,+\,\,{{H}_{2}}\,\,\to \,\,{{C}_{2}}{{H}_{6}}$ $\Delta H=\left( \sum :H_{f}^{0} \right)-{{\left( \sum H_{f}^{0} \right)}_{R}}$ $=\left( {{x}_{2}} \right)-\left( {{x}_{1}} \right)$