Calculating Molar Enthalpy of C2H4 Combustion w/ Hess's Law

[XxphysicsxX]

Homework Statement

Using Hess's Law and any necessary information from your Data Booklet, calculate the molar enthalpy of reaction for the combustion of ethene in kJ/mol.

im so lost!
i was going to find each sections molar en thalpy and then balance it but what's oxygens and do i multiply it by 3?

The Attempt at a Solution

C2H4 + 3 O2 --------------- 2CO2 + 2H2O

(+52.4)----->[2 x -393.5) + (2 x -285.8)] -[ 3 x 0)]


shouldnt there be three formulas basically?
so:
formation of 3O2 ------->
formation of 2H2O------>
formation of 2CO2------->

and then their enthalpy change?

then i balance all three and get the answer to


C2H4 + 3O2 ---> 2CO2 + 2H2O?

can someone help with the three fomulas please?thankyou!

 

[TeethWhitener]

Just make sure the formation enthalpy of ethylene is in there too and you should get the right answer.

 

[DrJohn]

Start from the elements making the compounds.

 

[Chestermiller]

Homework Statement

Using Hess's Law and any necessary information from your Data Booklet, calculate the molar enthalpy of reaction for the combustion of ethene in kJ/mol.

im so lost!
i was going to find each sections molar en thalpy and then balance it but what's oxygens and do i multiply it by 3?

The Attempt at a Solution

C2H4 + 3 O2 --------------- 2CO2 + 2H2O

(+52.4)----->[2 x -393.5) + (2 x -285.8)] -[ 3 x 0)]

This equation is incorrect. It should be

$\Delta H$ =[2 x -393.5) + (2 x -285.8)] -[ 3 x 0)]-[1 x 52.4]