Calculating Heat of Combustion for C2H6: Homework Statement Help

AI Thread Summary
The discussion focuses on calculating the heat of combustion for ethane (C2H6) using given reaction enthalpies. The user attempts to derive the heat of combustion by manipulating the provided equations and applying heats of formation. Initial calculations suggest a final answer of 1558.3 kJ, but the user questions its accuracy. Another calculation using heats of formation yields a different result of 1429 kJ/mol. The conversation emphasizes the importance of verifying calculations and the reliability of online tools for thermodynamic data.
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Homework Statement



Calculate the heat of combustion for C2H6 from the following information:
C2H4+ 3O2----> 2 CO2 + 2 H2O (-1409.5kJ)
C2H4 + H2 ----> C2H2 (-136.7 KJ)
H2 + 1/2 O2 -----> H2O ( -285.5 kJ)





The Attempt at a Solution



C2H6 --> C2H4 + H2 +136.7kJ
C2H4 + 302 --> 2CO2 + 2H20 -1409.5kJ
C2H6 + 3O2 --> 2CO2 + 2H2O + H2 -1272.8kJ
H2 + 1/2 O2 --> H2O -285.5Kj
C2H6 + 3.5O2 --> 2CO2 + 3H2O - 1558.3kJ


is my final answer 1558.3 correct?:confused: can someone check this for me pleasez
 
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It is close.
I have the following:
C2H6 + 2.5O2 --> 2CO2 + 3H2O + DH
Applying heats of formations for each compound:
-85 + 2.5*0 = 2*(-394) + 3*(-242) + DH
DH = 1429 kJ/mol

You may use the following calculator http://home.fuse.net/clymer/rq/ but I found it not being very accurate.
 
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