Question

Calculate the enthalpy change for:
C2H4(g) + H2 --> C2H6(g)

delta Hrxn:

H2(g) + 1/2O2 --> H2O (l)
C2H4(g) + 3O2 --> 2H20(l) + 2CO2(g)
C2H6(g) + 7/2O2(g) --> 3H20(l) + 2CO2(g)

I know I have to flip the third reaction but I don't know what to do next

Answer 1

Add equation 1 and equation 2 to the reverse of equation 3 and cancel molecules that appear on both sides of the equation to end up with the equation you want. For the dH rxn in this case add dH for 1 to dH for 2 to the negative dH for 3.

Answer 2

@k8Lbo3