# Find the standard enthalpy of formation of ethylene, C2H4(g), given the following data: C2H4(g) + 3O2(g)  -->  2CO2(g) + 2H2O(l)     H°rxn  = –1411 kJ Given that: H°f[CO2(g)] = –393.5 kJ/mol H°f[H2O(l)] = –285.8 kJ/mol

The standard enthalpy of formation of ethylene, C2H4(g), given the above data, is H°f(C2H4(g) =52.4 kJ/mol.

## Expert Answers The heat of reaction is the result of the breaking of bonds within the reactant species and the reforming of bonds to make the product species. The heat of formation (`Delta` H°f) is the energy required to form a compound in kilojoules per mole of substance. Heats of formation can be used to calculate the heat of reaction (`Delta` H°rxn) by subtracting the heats of formation of the reactants from the heats of formation of the products:

Heat of reaction = Heats of formation of products - Heats of formation of reactants

Heats of formation can be found in tables such as the one found here . Elements have a heat of formation of zero (they are the building...

(The entire section contains 2 answers and 387 words.)

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