# Heat of Combustion help!

by chemzz
Tags: combustion, heat
 P: 18 1. The problem statement, all variables and given/known data 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) 3. 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? can someone check this for me plzz
 P: 1 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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