calculate the standard enthalpy of formation of ethene (C2H4)from the following equation-
C2H4(g) + 3O2(g)-----》 2CO2 +2H2O enthalpy of formatiom of reaction is -1323 kJ/m
Enthalpy of formation of CO2,H2O and O2 are -393.5 ,-249,0 respectively
First let us consider the combustion reaction given that is,
C2H4(g) + 3O2(g)---à 2CO2(g) +2H2O(g)
Let us first calculate enthalpy of formation of CO2 and H2O on RHS of reaction from the given data.
= 2(-393.5)+2 (,-249)
= -(787 + 498)
= -1285 kJ/mol.
This means -1358.6 kJ of energy released in the formation of CO2 and H2O.
In the LHS of the reaction one mole of C2H4 is formed first and then reacted with 3 moles of oxygen to give products. But the enthalpy of formation of O2 is given 0, hence
= + 3(0)
Enthalpy of formation of ethene is given by