# Homework Help: Simple chem equation

1. Mar 14, 2005

### a_ng116

What is the equation for the heat of formation for propanol?

2. Mar 14, 2005

### dextercioby

What reaction...?

Daniel.

3. Mar 14, 2005

### a_ng116

Sorry. The whole question was:

If the heat of combustion of propanol is -1843.7 kJ/mol, what is the heat of formation of propanol? Write the equation for the heat of formation for propanol and include the energy as a term in the equation.

I got the heat of formation to be -304 kJ. I'm not too sure how to write the equation though.

4. Mar 14, 2005

### xanthym

Propanol Combustion:
C3H8O(l) + (9/2)O2(g) → 3CO2(g) + 4H2O(g) ::: DHc=(-1843.7 kJ/mol)

Propanol Formation:
We begin with the Propanol Combustion "reverse" reaction and add other formation reactions required to obtain the Propanol Formation equation (in RED below). During the "addition" process, entities on both sides of the equation will "cancel".

3CO2(g) + 4H2O(g) → C3H8O(l) + (9/2)O2(g) ::: DHr=(+1843.7 kJ/mol)*(1)=(+1843.7 kJ)
3C(s) + 3O2(g) → 3CO2(g) ::: DHf=(-393.9 kJ/mol)*(3)=(-1181.7 kJ)
4H2(g) + 2O2(g) → 4H2O(g) ::: DHf=(-241.8 kJ/mol)*(4)=(-967.2 kJ)
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3C(s) + 4H2(g) + (1/2)O2(g) → C3H8O(l) ::: DHf=(-305.2 kJ/mol)

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Last edited: Mar 14, 2005