When ethylene is heated with 1.5 moles  of oxygen the heat liberated is 702kJ. Enthalpy of combustion of ethylene is 

${\mathrm{C}}_2{\mathrm{H}}_4\left(\mathrm{g}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)\stackrel{ }{\to }2{\mathrm{CO}}_2\left(\mathrm{g}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathcal{l}\right);\mathrm{\Delta H}=?$

This equation represents  combustion of ethylene

1.5 moles of ${\text{O}}_2$when reacts with ethene liberates 702kJ

3 moles of ${\mathrm{O}}_2$when reacts with ethene liberates _____

${\mathrm{\Delta H}}_{\mathrm{combustion}}=2(-702)=-1404\mathrm{kJ}$