Determining Heat of Formation of n-Butane

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The standard heat of formation for n-butane cannot be measured directly but can be calculated using Hess's law and combustion data. The combustion reactions for carbon, hydrogen, and n-butane in oxygen are provided, and the user attempts to derive the formation equation for n-butane, struggling with balancing the oxygen atoms. The user also inquires about the standard molar enthalpy of formation for propanol, questioning the correct chemical equation. Feedback indicates that the proposed equations are unbalanced and use non-standard states. The discussion emphasizes the importance of correctly balancing chemical equations in thermodynamic calculations.
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Homework Statement



The standard heat of formation of n butane cannot be measured directly but can be determined indirectly from other heats of reaction by applying hess's law. Given the folowing data for the combustion of carbon hydrogen and n butane in oxygen:

C + O2---> CO2 H=-393.5
H2 + 1/2O2 --> H2O
C4H10 + 6.5O2 ---> 4CO2 + 5H2O

Homework Equations





The Attempt at a Solution



Tried several times on scratch paper. The formation of butane is as so : 4C + 5H2-->C4H10

Ive tried the actual formation using CO2 + H2O --> C4H10 But i can't cancel the carbons

Sticking with my other normal equation 4C + 5H2 --> C4H10 (This is what I want, No?)

Tell me if my equation is wrong, cause it proabably is.

I tried multiplying the first step by 4, the second step by 5, and reversing the third step only to get everything to cancel except the oxygen. I get stuck with 6.5 oxygens on the left side and 9.5 Oxygens on the right. Dont know where to g ofrom there. Help please!
 
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4 \times 1 + 5 \times \frac 1 2 = 6.5
 
elaborate...?
 
Here is another question: Write the chemical equation for the standard molar enthalpy of formation of proponol. c3h8O
Is this simply :: 3C + 8H + O2 ----> C3H8O ( I am pretty sure its this one.)

?

Or is it 3CO2 + 4H2O ----> C3H8O + 9/2O2

Thanks
 
Nellen2222 said:
elaborate...?

Where did you get 9.5 molecules of oxygen from?
 
Nellen2222 said:
Is this simply :: 3C + 8H + O2 ----> C3H8O ( I am pretty sure its this one.)

It is not balanced and it uses substances in non standard state. But it is much better than the other one.
 
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