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# Hess law chemistry question (HELP) watch

1. Find the enthalpy change for the following reaction using the bond enthalpy data below:

C2H6+3 1/2 O2 -> 2CO2 + 3H2O

C-C= 348
C-H= 412
O=O= 496
C=O= 743
O-H= 463

really lost what to do especially cause the data the question says dosent say enthalpy change of combustion on enthalpy change formation

also why is it mixing in with organic chemistry when they give us a normal equation , someone help plz
2. So i think if i draw the molecular diagram for ethane and the other , would that work ?
3. someone plz
Find the enthalpy change for the following reaction using the bond enthalpy data below:

C2H6+3 1/2 O2 -> 2CO2 + 3H2O

C-C= 348
C-H= 412
O=O= 496
C=O= 743
O-H= 463

really lost what to do especially cause the data the question says dosent say enthalpy change of combustion on enthalpy change formation

also why is it mixing in with organic chemistry when they give us a normal equation , someone help plz
It's a question where you need to do
enthalpy change = energy needed to break bonds- energy given out making bonds.
5. (Original post by Gregor99)
It's a question where you need to do
enthalpy change = energy needed to break bonds- energy given out making bonds.
what do i put on the bottom bit of the hess law triangle thing and what do i put on each one , idk what to do
6. It is not Hess's law
7. You work out the energy used for bonds breaking
The energy released from new bonds being made then use the equation I have stated above.
This may have been a method you used at GCSE
Find the enthalpy change for the following reaction using the bond enthalpy data below:

C2H6+3 1/2 O2 -> 2CO2 + 3H2O

C-C= 348
C-H= 412
O=O= 496
C=O= 743
O-H= 463

really lost what to do especially cause the data the question says dosent say enthalpy change of combustion on enthalpy change formation

also why is it mixing in with organic chemistry when they give us a normal equation , someone help plz
This is not Hess's law, this is bond enthalpies. Remember break-make (minus the bonds made from the bonds formed).
9. (Original post by Gregor99)
It is not Hess's law
(Original post by Gregor99)
You work out the energy used for bonds breaking
The energy released from new bonds being made then use the equation I have stated above.
This may have been a method you used at GCSE
(Original post by EdexcelAreIdiots)
This is not Hess's law, this is bond enthalpies. Remember break-make (minus the bonds made from the bonds formed).
well i'm thick af , ik what u guys mean now but i got confused cause my teacher literally gave us this sheet with a tittle saying hess's law calculations an question 1 has little to nothing to do with it , thanks guys XD

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Updated: February 7, 2018
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