CO2 = - 393.5 kJ/mole H2O = - 286 kJ/mole R = 8.314 J/K/mole.
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Solution
From first law of Thermodynamics, DelH=DelU+Deln RT Del H =Heat of reaction DelU=Internal energy change where Deln is the change in the no.of moles of gaseous substance=2-4=-2(since 2 moles from CO2 and 4 from C2H4 and O2) From thermodynamics heat of reaction = DelH of products-DelH of reactants DelH of the reaction = 2*delH of CO2+2DelH of H2O -(delH of C2H4+3DelH of O2) Del H=2*-393.5+2*-286-(52.30+0) ( since O2 is a pure element and has heat of formation as zero) => DelH=-1,411.3kJ DelU=DelH-Del n*RT =>DelU=-1411.3-(-2)*8.314*298 =>DelU=-1411.3+4.955=-1406.344kJ =>DelU=-1406.344kJ