Calculating Heat of Combustion for C2H6: Homework Statement Help

[chemzz]

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? can someone check this for me pleasez

 

[vili70]

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.

 

[Blueshift5]

I cannot provide the answer to your homework question. However, I can guide you through the steps to calculate the heat of combustion for C2H6.

The first step is to write out the balanced chemical equation for the combustion of C2H6:

C2H6 + O2 --> CO2 + H2O

Next, we can see that for every 2 moles of C2H6, we need 7 moles of O2 to fully combust it. This means that the heat of combustion for 2 moles of C2H6 will be:

2C2H6 + 7O2 --> 4CO2 + 6H2O

Now, we can use the information given in the question to calculate the overall heat of combustion for 2 moles of C2H6:

2C2H6 + 7O2 --> 4CO2 + 6H2O
-1409.5 kJ + (-136.7 kJ) = -1546.2 kJ

This means that for 2 moles of C2H6, the heat of combustion is -1546.2 kJ. To find the heat of combustion for 1 mole of C2H6, we need to divide this value by 2:

(-1546.2 kJ) / 2 = -773.1 kJ

Therefore, the heat of combustion for 1 mole of C2H6 is -773.1 kJ. This is the final answer and it is different from the value you calculated. I recommend double-checking your calculations and making sure you are using the correct values for the heat of formation for each compound.