The enthalpy of formation of ethane ( C_2 H_6) from ethylene by addition of hydrogen where the bond-energies of C-H, C-C, C=C, H-H are 414 kJ, 347…

The enthalpy of formation of ethane $\displaystyle \left(\mathrm{C}_2 \mathrm{H}_6\right)$ from ethylene by addition of hydrogen where the bond-energies of C-H, C-C, C=C, H-H are $\displaystyle 414$ kJ, $\displaystyle 347$ kJ, $\displaystyle 615$ kJ and $\displaystyle 435$ kJ respectively is - $\displaystyle \_\_\_\_$ kJ